Columtiia  ©mbers^itp  . 
in  tije  Citp  of  ileto  |9orfe      i ' 

COLLEGE  OF  PHYSICIANS 
AND   SURGEONS 


Reference  Library 

Given  by 


v^jft^ii*  r^  ^-5^^ 


Digitized  by  tine  Internet  Archive 

in  2010  witii  funding  from 
Columbia  University  Libraries 


http://www.archive.org/details/directionsforlabOOIomb 


DIRECTIONS 


Laboratory  Work  in  Physiology 


FOR  THE  use;  op 


MEDICAL  STUDENTS 


WARREN  P.  IvOMBARD,  A.  B.,  M.  D. 

PROFESSOR    OF    PHYSIOLOGY,    UNIVERSITY    OF    MICHIGAN 


SECOND  EDITION 


GEORGE  WAHR,  PaBLisHER 

ANN   ARBOR 


Copyright,   1914 

BY 

GEORGE)  WAHR 


7YU:JL 


arvi- 


RBOR    PRESS 


PREFACE 

Every  one  who  has  attempted  to  plan  a  short  course 
of  physiological  experiments  for  Medical  students,  has  had 
to  face  the  fact  that  only  a  few  of  the  many  experiments 
which  would  be  desirable,  can  be  satisfactorily  performed 
in  the  alloted  time.  The  course  here  outlined  contains 
only  such  experiments  as  can  actually  be  made  and  properly 
studied  by  the  student  himself,  working  three  and  a  half 
hours  a  day  for  35  days.  An  additional  week  is  spent  in 
extra  work  and  examinations.  Since  the  students  for  whose 
use  this  book  has  been  especially  prepared,  have  a  special 
course  in  physiological  chemistry,  and  are  taught  the  physi- 
ology of  the  eye,  etc.,  in  connection  with  the  demonstration 
courses  devoted  to  the  specialties,  to  avoid  duplication,  ex- 
periments  dealing  with  these   subjects  have  been  omitted. 

The  experiments  are  arranged  so  as  first  to  teach  the 
student  the  use  of  the  graphic  method,  time  recording  in- 
struments, and  the  electrical  apparatus  employed  for 
excitation.  At  the  same  time  he  becomes  acquainted  with 
the  genera!  physiology  of  striated,  non-striated,  and  heart 
muscle  and  of  the  nerves  of  the  frog.  He  then  studies 
the  reaction  of  his  own  muscles  and  nerves  to  various 
forms  of  electrical  excitation.  Throughout  this  work,  spe- 
cial attention  is  called  to  the  errors  which  the  apparatus  it- 
self may  introduce  into  the  graphic  records :  the  need  of  ac- 
curacy of  measurements ;  the  value  of  expressing  the  figures 
obtained  in  plotted  curves ;  the  importance  of  promptly  writ- 
ing up  the  notes  taken  during  the  experiments ;  and  the  fact 
that  the  reports  given,  should  state  what  was  observed  by  the 
student  himself,  rather  than  what  is  written  in  text  books. 
The  latter  half  of  the  course  deals  with  the  problems  of 
respiration,  the  circulation,  the  central  nervous  system,  etc. 

Only  two  afternoons  are  given  to  experiments  on  warm 
blooded    animals,   but    the    experiments    with    the    artificial 


iv  PREFACE 

circulation  apparatus,  a  special  quiz  on  the  subjects  to  be 
covered,  and  a  "dress  rehersal"  with  the  apparatus,  have 
so  prepared  the  way,  that  even  in  this  short  time,  many 
of  the  most  important  facts  relating  to  the  circulation, 
respiration  and  peristalsis  are  observed. 

It  is  believed  that  the  medical  student  should  as  far 
as  is  possible,  study  the  physiology  of  man,  and  during 
more  than  a  third  of  the  course,  the  student,  himself,  is 
the  subject  of  the  experiment.  It  is  needless  to  say  that 
the  frogs  are  rapidly  killed  before  being  used,  and  that 
the  mammals  employed  are  thoroughly  anaesthetized  by 
the  student,  under  the  direction  of  an  instructor. 

As  most  of  the  students  taking  the  course  have  no 
knowledge  of  physiological  methods,  the  directions  for  the 
work  have  been  made  as  explicit  as  possible  with  the  object 
of  saving  time.  Nevertheless,  the  harm  which  comes  from 
machine-like  work  is  fully  recognized,  and  students  are  en- 
couraged to  cultivate  independence,  and  permitted  to  per- 
form the  experiments  in  other  ways  than  those  called  for 
in  the  notes.  They  are  made  to  feel  that  the  capacity  to 
observe  and  correctly  interpret  the  results  of  an  experi- 
ment, is  of  even  more  importance  than  the  ability  to  make 
an  experiment  successfully,  and  that  one  who  has  trained 
his  powers  of  observation  and  has  learned  to  accurately 
report  the  phenomena  he  has  witnessed,  can  i^iake  a  re- 
liable diagnosis  and  keep  a  trustworthy  case-book. 

The  library  of  the  laboratory  contains  many  journals, 
books,  monographs  and  reprints,  and  the  instrument  room 
holds  many  forms  of  apparatus  especially  designed  for  re- 
search work.  Every  facility  of  the  laboratory  is  placed  at 
the  disposal  of  those  who  show  that  they  are  capable  of 
independent  work. 

This  edition  contains  a  number  of  experiments  not  found 
in  the  first,  while  the  directions  for  many  of  the  other  ex-, 
periments  have  been  practically  rewritten.  Ten  new  illus- 
trations have  been  added. 

It  gives  me  great  pleasure  to  acknowledge  the  aid 
which  I  have  received  in  developing  the  methods  employed 
in  this  course  from  the  former  instructors  and  assistants 


PREPACK  V 

in  this  department,  and  especially,  from  Professor  S.  P 
Budgett,  Professor  A.  E.  Guenther,  Dr.  G.  G.  Crosier, 
Professor  W.  P.  Bowen,  Professor  C.  J.  Wiggers,  Dr.  F. 
M.  Abbott,  Dr.  N.  N.  Wood,  and  Professor  W.  F.  Koch. 
I  am  particularly  indebted  to  Dr.  Otis  M.  Cope  for  his 
help  in  the  preparation  of  this  edition. 

WARREN  PLIMPTON  LOMBARD. 
Physiological  Laboratory 
University  of  Michigan 
July  I,  1 9 14, 


CONTENTS. 

General  directions.  Instruments,  etc.,  to  be  purchased 
by  students.  List  of  apparatus  to  be  supplied  by 
the  laboratory.  The  bulletin  board.  Method  of 
work. .  ,     XIX 

Experiment  I. 

Extensibility  and  Elasticity  of  a  steel  spring.        .        .        i 
Mounting  of  curves. 
The  student's  notes. 

Experiment  II. 

Extensibility  and  Elasticity  of  frog's  muscle.  .        .        7 

Method  of  killing  frog. 
Muscle  preparation. 

a.  Experiment. 

b.  Plotting  of  curves. 

J^XPERTMENT  in. 

Response  of  muscle  to  making  and  breaking  induction 
shocks  of  various  strengths,  and  use  of  the  short- 
circuiting  key.  13^ 

Some  facts  regarding  the  induction  apparatus : 

a.  Response  to  making  and  breaking  shocks  of  in- 
creasing strength. 

b.  Use  of  the  short-circuiting  key. 

Experiment  IY. 

Relation  of  amount  of  load  to  height  of  Hft  and  quan- 
tity of  v.'ork  done. .21 

a.  Experiment. 

b.  Plotting  of  curves. 


"VIU  CONTENTS. 

EXPICRIMENT   V. 

Fatigue  of  Human  Muscle. 25 

a.  Effect  of  slow  rate. 

b.  Effect  of  quick  rate. 

c.  Effect  of  rest. 

d.  Effect  of  massage. 

Experiment  VI. 

'Time  relations  of  myogram 29 

a.  Influence  of  rate  of  drum  on  form  of  myogram. 

b.  Time  relations  of  myogram. 

c.  Measurement    of    records    and    computation    of 

time  intervals. 

Experiment  A^II. 

•Genesis  of  tetanus 35 

a.  Summation  of  two  contractions. 

b.  Incomplete  tetanus  and  complete  tetanus. 

c.  Complete  tetanus   obtained   with   automatic   in- 

terrupter. 
Electrical  connections  in  primary  circuit  of  induc- 
tion apparatus. 

d.  Fatigue  caused  by  tetanus. 

Experiment  VIII. 
Rate  of  tapping 43 

Experiment  IX. 

Independent  irritability  of  muscle.  .        .        .    •     .     47 

Method  of  pithing  frog,  and  of  injecting  curara. 

Experiment  X. 

Isolated  conduction  in  muscle.  53 

Method  of  unipolar  excitation. 


CONTENTS.  ix: 

Experiment  XI. 

Contractions  of  non-striated  muscle 57" 

a.     Time  relations  of  the  myogram, 
h.     Rate  required  to  tetanize. 
c.     Spontaneous  contractions.- 

Experiment  XTT. 

The  frog's  heart ;  its  structure  ;  the  relative  time  of  ac- 
tion of  the  different  parts.  .        .        .        .      6r 

a.  Gross  anatomy  of  frog's  heart. 

b.  Origin  and  course  of  the  wave  of  contraction. 

1.  Inspection. 

2.  The  myocardiogram. 

Experiment  XIII. 

Effect  of  Temperature  on  Heart  Rate 67 

a.  Effect  of  air. 

b.  Effect  of  solutions. 

Experiment  XIV. 
Refractory  period  and  compensatory  pause.     .        .        •     7r 

Experiment  XV. 

Response  of  resting  heart  to  stimulation  by  induction 

shocks y^. 

a.  Myogram  of  heart  muscle. 

b.  Bowditch's  staircase. 

c.  All  contractions  maximal. 

d.  Effect  of  frequent  stimuli. 

Experiment  XVI. 

Location  of  a  few  motor  points  on  the  human  arm.        .      79 
The  more  efficient  pole  of  an  induction  coil. 


x  contents. 

Experiment  XVIT. 
Response  of  human  muscle  to  separate  induction  shocks 

and  to  a  tetanizing  current.  ....     85 

•     a.     Making  and  breaking  induction  shocks  of  vari- 
ous' strengths, 
b.     Tetanizing  current. 

Experiment  XVIIT. 
Galvani's  experiment. 91 

Experiment  XIX. 

Polarization  of  electrodes. 95 

a.  Polarizable  electrodes. 

b.  .N'on-polarizable  electrodes. 
Pfliiger's  Law. 

Experiment  XX. 

Response  of  nerve  to  opening  and  closing  of  the  direct 
battery  circuit,  with  currents  of  various 
strengths. loi 

Experiment  XXT. 
Stimulation  of  human  nerves  b_y  the  direct  current.        .    105 

Experiment  XXII. 

Currents  of  rest  and  action iii 

a.  Current  of  rest  detected  by  a  rheoscopic  frog 

preparation. 

b.  Current  of  action  detected  by  a  rheoscopic  frog 
preparation. 

Experiment  XXIII. 

The  reflex  frog 115 

a.  Time  of  recovery  from  shock. 

b.  Spread  of  reflexes. 

c.  Are  reflexes  purposeful? 

d.  Reflex  time. 

e.  Spasm    of    muscles    versus    coordinated    move- 
ments. 


CONTlvNTS.  XI 

Experiment  XXIV. 
Reaction  time  for  sound 119 

Experiment  XXV. 

Cutaneous  sensations  and  muscle  sense.  .        .        .    123 

a.  Cold  and  warmth  spots. 

b.  Tickle  and  pressure  spots. 

c.  Pain  spots. 

d.  Muscle  sense. 

Experiment  XXVT. 

The  knee-jerk  as  modified  by  reenforcing  and  inhibiting 

influences. 129 

a.  Record  of  normal  knee-jerk. 

b.  Motor  reenforcements. 

c.  Reenforcement  by  sensory  stimuli. 

d.  Psychic  reenforcements. 

Experiment  XXVII. 

Co'nditions  determining  the  blood  pressure  and  the  ve- 
locity of  flow. 137 

Artificial  circulation  apparatus. 

part  I. 

Arterial  and  venous  pressure. 

a.  Effect  of  inertia  of  mercury. 

b.  Effect  of  rate. 

c.  Effect  of  increased  output. 

d.  Eftect  of  resistance. 

e.  Effect  of  resistance  in  two  systems  of  arteries  on 

distribution. 

f.  Some  clinical  applications  : 

I.     Effect  of  vagus  inhibition. 


Action  of  depressor  nerve. 
Traube-Hering  waves. 
Nitrite  of  Amyl. 
Hardening  of  wall  of  artery. 


xn  CONTENTS. 

PART  II. 

Intra-ventricular  pressure  and  arterial  pulse. 

a.  Effect  of  rate. 

b.  Effect  of  volume  output. 

c.  Effect  of  peripheral  resistance. 

PART  III. 

Lesions  of  Heart  VaWes. 

a.  Mitral  stenosis. 

b.  Aortic  stenosis. 

c.  Mitral  insufficiency. 

d.  Aortic  insufficiency. 

ExPERIMIvNT  XXVTII. 

Circulation  and  respiration  of  the  mammal.       .      .        .151 
Schedule  of  work.     List  of  apparatus.     Directions 
to  student  caring  for  apparatus.     Directions  to 
Assistant.      Anaesthesia.      Directions    to    anses- 
thetizer.     Directions  to  operator. 

a.  Measure  of  blood  pressure  in  the  carotid. 

b.  Excitation  of  the  peripheral  end  of  the   right 
vagus. 

c.  Excitation  of  central  end  of  right  vagus. 

d.  Excitation  of  peripheral  end  of  left  vagus. 

e.  Excitation  of  sciatic  nerve. 

f.  Blood  pressure  during  asphyxia. 

g.  Elasticity  of  lung  tissue. 

Experiment  XXIX.    , 

Circulation  and  respiration  of  the  mammal  continued.   167 

a.  Excitation  of  right  depressor  nerve. 

b.  Excitation  of  left  depressor  nerve. 

c.  Tracheotomy  and  artificial  respiration. 

d.  Current  of  action  of  the  heart. 

e.  Observation  of  exposed  heart  during  vagus  ex- 

citation. 

f.  Tension  of  ventricle  during  systole  and  diastole. 


CONTENTS.  •  xiii 

g.     Observation    of    the    changes    in    heart    during 

death  from  asphyxia, 
h.     Innervation  of  diaphragm  by  the  phrenic  nerves, 
i.      Peristalsis  of  intestine. 

Expkrim£;nt  XXX. 

Carotid  pulse  in  man. 173 

Form  of  the  pulse  curve,  and  effect  of  arterial  pres- 
sure. 

a.  The  pulse  rate. 

b.  Duration  of  systole  and  diastole. 

c.  Effect  of  exercise. 

Experiment  XXXI. 

The  radial  pulse  studied  by  the  tambour  method.    .        .    181 

a.  Form  of  radial  pulse. 

b.  Postponement  of  the  radial  pulse. 

Experiment  XXXII. 

The  radial  pulse  as  recorded  by  the  Jacquet  Sphygmo- 

graph. 185 

a.  Normal  curves  and  effect  of  position  of  body. 

b.  Effect  of  compressing  brachial  artery. 

c.  Effect  of  deglutition. 

d.  Effect  of  inhalation  of  Amyl  Nitrite. 

e.  Valsalva's  experiment. 

f.  Miiller's  experiment. 

Experiment  XXXIII. 

Capillary  circulation  in  the  web  of  the  foot  of  a  frog.   191 

I.  In  small  artery. 

II.  In  small  vein. 

III.  In  capillaries. 

IV.  Vaso-motor  action. 

V.  Diapedesis. 

VI.  Capillaries  of  human  skin. 


XIV  CONTENTS. 

Experiment  XXXIV. 

Cilia 195 

a.  Work  of  cilia. 

h.  Effect  of  temperature. 

c.  Microscopic  examination. 

Experiment  XXXV. 

Measurement  of  systolic  and  diastolic  pressure  in  hu- 
man arteries. 199 

Systolic  pressure. 

a.  Tactile  criterion. 

b.  Auscultatory  criterion. 

c.  Criterion  of  sudden  rise  of  pulse  record. 

d.  Criterion  of  pulse  form. 
Diastolic  pressure. 

a.  Auscultatory  criterion. 

b.  Largest  pulsation  criterion. 
Experiment. 

I.  Systolic  pressure  ; — tactile  criterion. 

a.  Subject  seated. 

b.  Subject  standing. 

c.  Effect  of  exercise. 

II.  Systolic  and  diastolic  pressures;  —  auscultatory 

method. 

a.  Systolic  pressure. 

b.  Diastolic  pressure. 

III.  Systolic    and    diastolic    pressures; — tambour 

method. 

a.  Systolic  pressure. 

b.  Diastolic  pressure. 

Experiment  XXXVI. 

Conditions  changing  the  volume  of  hand.       .        .        ,211 

a.  Tickling. 

b.  Pain. 

c.  Psychic  excitation. 

d.  Cold. 


CONTENTS.  XV 

Experiment  XXXVII. 
Venous  pressure  in  man 215 

Experiment  XXXVIII. 
Pulse  in  large  veins  of  man 219 

Experiment  XXXIX. 

The  normal  sounds  of  the  heart 223 

a.  Auscultation  over  the  lower  part  of  the  chest. 

b.  Auscultation  over  the  base  of  the  heart. 

c.  Time    relations    of    heart    sounds,    cardiogram, 

pulse  curve. 

Experiment  XL. 

Thoracic  and  abdominal  movements  in  respiration.       .   231 

a.  Normal  record. 

b.  Effect  of  using  the  voice. 

c.  Inhibitory  effects  of  swallowing. 

d.  Effects  of  effort. 

e.  Relation  of  rate  of  respiration  to  rate  of  heart. 

Experiment  XLI. 

Measurement  of  expired  air 235 

a.  Tidal  air. 

b.  Supplemental  air. 

c.  Vital  capacity. 

d.  Complemental  air. 

Experiment  XLII. 

Regulation  of  body  temperature.       .        .        .        .        .   241 

a.  Loss  of  heat  from  skin. 

b.  Loss  of  heat  from  air  passages. 

Experiment  XLIII. 

Artificial  respiration 245 

a.  Schaefer's  method. 

b.  Effect  of  apnoea. 

c.  Sylvester's  method. 


ILLUSTRATIONS. 

I.     Apparatus  for  recording  the  extensibility  and  elas- 
ticity of  a  steel  spring. i 

-   2.     Apparatus  for  recording  the  extensibility  and  elas- 
ticity of  a  frog's  muscle 8 

3.  Apparatus  for  recording  contractions  of  a  frog's 

muscle,  excited  by  induction  shocks.     ...      13 

4.  Curve  of  lift  and  of  work.         .        .        .        .        .21 

5.  Apparatus   for  automatically  exciting  muscle,  by 

letting  the  drum  open  the  key 29 

6.  Method  of  preparing  myogram  for  determination 

of  latent  period 32 

7.  Apparatus  for  studying  summation  of  contractions.     35 

8.  Scheme  of  electrical  connections  of  primary  coil 

in  two  forms  of  induction  apparatus.         .        .      37 

9.  Relation  of  brain  to  skull  of  frog 47 

10.  Dissection  of  right  leg  of  frog 48 

11.  Diagram  of  experiment  on  the  action  of  curara     .  49 

12.  Apparatus  recording  beats  of  a  frog's  heart.         .  61 

13.  The  gross  anatomy  of  a  frog's  heart.        ...  63 

14.  Apparatus  to  detect  direction  of  flow  of  current  in 

a  simple  circuit 79 

15.  ■   Apparatus  to  detect  direction  of  flow  of  current 

in  secondary  coil  of  an  induction  apparatus.       .     80 

16.  Apparatus     for    unipolar    excitation    of     human 

nerves,  with  an  induced  current.  .        .        .81 

17.  Diagram  of  location  of  motor  points  on  flexor  side 

of  arm,  (after  Erb.) 81 

18.  Arm  rest  for  support  of  hand  and  electrodes.       .     85 

19.  Apparatus    for   recording   movements    of   thumb.     86 

20.  Apparatus  for  Galvani's  experiment.       .        .        -9^ 

21.  Method   of   arranging   non-polarizable   boot   elec- 

trodes in  moist  chamber 97 

22.  Diagram  to  illustrate  Pfliiger's  law.         ...     98 
27,.     Method  of  using  rheocord.       .  10 1 


XVlil  ir.UJSTRATlONS. 

24.  Ap'paratus   for  stimulating  human  nerves  by  the 

direct  current. 105 

25.  Diagram  of  the  course,  and  of  the  effects  of  the 

direct  current,  applied  through  the  skin  tO'  the 
nerves  of  man. 107 

26.  Apparatus  for  recording  reaction  time  to  sound.   119 

27.  Diagram  of  nervous  paths  followed  by  the  nerve 

impulses  causing  the  knee-jerk  and  its  reen- 
forcements 129 

28.  Method  of  supporting  thigh  and  foot,  and  of  re- 

cording the  swing  of  the  lower  leg,  in  the  knee- 
jerk  experiment 131 

29.  Artificial  circulation  apparatus.         .        .        .        .137 

30.  Recording  tambour 145 

31.  Scheme  of  apparatus  for  studying  the  blood  pres- 

sure of  a  mammal. 153 

32.  Dissection  of  nerves  of  left  side  of  neck  of  rabbit.   159 

33.  Method  of  inserting  cannula  into'  carotid  artery.   160 

34.  vSphygmogram  of  a  normal  and  of  a  dicrotic  pulse.   173 

35.  Diagram  of  a  high  and  of  a  low  pressure  pulse.   175 

36.  Tambour  and  neck  spring  used  to  study  the  hu- 

man carotid  pulse. 176 

37.  Method  of  applying  tambour  to  wrist,  to  obtain 

sphygmogram  from  the  radial  artery.  .        .    181 

38.  Scheme  of  Jacquet's  sphygmograph.        .  .        .    185 

39.  Laborator}^  form  of  sphygmomanometer.  .        .   201 

40.  Diagram    of    changes    in    brachial    artery  during 

measurement  of  systolic  and  diastolic  pressures.  203 

41.  Diagram  of  heart  cycle,  shoAving  changes  of  form 

of  the  right  heart,  and  their  relation  to  the  ven- 
ous pulse,  carotid  pulse  and  heart  sounds.         .   221 

42.  Diagram  showing  position  of  heart  in  chest,  posi- 

tion of  valves  as  projected  on  wall  of  chest,  and 
the  parts  of  the  chest  where  the  sounds  of  the 
heart  are  heard  best 223 

43.  Diagram   of    heart    cycle,    indicating   changes    of 

form  of  the  right  heart,  versus  the  cardiogram, 
the  venous  pulse,  the  carotid  pulse,  and  heart 
sounds.  . 229 

44.  Apparatus  for  measuring  the  expired  air.       .        .   237 


GENERAL  DIRECTlONvS. 


genp:ral  directions 

The  laboratory  hours  are  from  half  past  one  to  five 
o'clock.  Each  student  must  have  receipts  from,  the  Treas- 
urer, to  show  that  the  laboratory  fee  and  the  key  deposit 
have  been  paid,  and  each  must  have  the  following  articles 
before  beginning  the  work : 

Laboratory  text  book. 

2   celuloid  triangles    (6-inch). 

Dividers. 

Flesh  pencil. 

Forceps  with  fine  point. 

Reading  glass. 

MM  rule,   lo  cm.  long. 

Strong  scissors  with  fine  points. 

2  towels. 

Tube  of  office  paste. 

2  sheets  of  millimeter,  cross  section  paper. 

40  sheets  of  note  paper,  regulation   size. 

40  sheets  of  cardboard,  regulation  size. 

Two  students  will  work  together,  and  students  are 
advised  to  choose  their  partners  early.  A  list  of  the  fol- 
lowing apparatus  will  be  supplied  by  an  instructor,  when 
the  two  students  who  are  to  work  together  present  the 
Treasurer's  receipts,  and  show  the  instruments,  etc.  which 
are  required  in  the  course.  The  list  is  to  be  checked  and 
signed  by  both  of  the  students  who  are  to  use  the  apparatus. 
Larger,  special  pieces  of  apparatus  will  be  supplied  from 
time  to  time  when  needed. 

APPARATUS    SUPPLIED   BY   LABORATORY 

Division  A. 

Acetic  acid,  10%.  2   Clamps,   cabinet  maker's. 

Basin.  Clamp,   large   muscle. 

l-!attery  jar.  .  6  Clamps  for  rods. 

Board    for   frog.  Coil,   aluminum. 

Brush   for  salt  solution.  Cloth  to  cover  apparatus. 

Two  cells,  dry.  Dropper. 

Clamp,    burette.  Drum  square. 


XX 


GENDRAI^  DIRKCTIONS. 


Electrodes,  boot  form  in  dish. 

Electrode,  brass. 

Electrode,  heart. 

Electrode,  pin. 

Electrode,  platinum. 

Electrode,  sheet  of  copper. 

Filter   paper. 

Finger  piece,  wooden. 

Fork  and  yoke. 

2.  Glasses,  drinking. 

Glass  dish   for  salt  solution. 

Glass  slide  on  support. 

Hook  for  frog. 

Hooks,  pin. 

Induction  coil. 

Key,  mercury. 

Key   opener. 

Kymograph  and  drum. 

Lever,  heavy. 

Lever,   light. 

Ligatures. 

Moist  chamber  with  two  clamps. 

2  pads,  gauze. 


Pins. 

Plate. 

Pulley. 

Rod,  glass,  with  clips  for  boots. 

Rod,  L,  nickeled. 

Rod,  screw  in  end. 

Rod,  zinc. 

Rubber  band,  large.   . 

2  Rubber  bands,  thin. 

2  Signals,  electric. 

Spring,   steel,   with  pointer. 

Stand,  long. 

Stand,  short. 

Sodium   chloride,   0.6%. 

Sulphuric   acid,  o.i%. 

Thread,   silk. 

20  Weights,   10  gram. 

1  Wire,  insulated,  extra  long. 
4  Wires,  insulated,  medium. 

2  Wires,  insulated,  short. 
Zinc  sulphate. 

2  Zincs  for  electrodes. 


Division  B. 


Board  for  frog. 

Brush  for  salt  solution. 

Cell,  dry. 

5  clamps,  for  rod. 

1  Clamp,   cabinet   maker's. 
Cloth  to  cover  appratus. 
Coil,  aluminum. 

Drum  square. 
Electrodes,  pin. 
Filter  paper. 
F'ork,  with  yoke. 

2  Glasses,  drinking. 

Glass  dish  for  salt  solution. 

2  Hooks,  pin. 

Induction  coil. 

Key,  mercury. 

Key  opener. 

Kjanograph   with   drum,   4   fans. 

Lever,  light. 

Lever,  heavy. 


Moist  chamber  with  clamp. 

Pins. 

2  Pinch  cocks. 

Plate. 

2  Pneumographs. 

Rod,  L,  nickeled. 

2  Rubber  tubes,  with  glass  Ts. 

Signal,    electric. 

Sodium  chloride,  0.6%. 

Spring,  steel,  with  pointer. 

Stand,  long. 

Stand,  short. 

Tambour,  carotid  with  spring. 

Tambour,  radial. 

2   Tambours,   recording. 

Thread,-  silk. 

20  Weights,   10  gram. 

5  Wires,  insulated,  long. 

2  Wires,  insulated,  medium. 


Students  are  to  use  the  apparatus  supplied  them,  and 
no  other.  In  no  case  is  apparatus  to  be  taken  from  the 
shelves  or  borrowed  from  other  students. 


GENERA!.  DIRECTIONS.  XXI 

THE   BUEEETIN    BOARD 

The  bulletin  board  near  the  door  of  the  main  laboratory- 
is  arranged  as  follows :  Horizontal  lines  give  the  work  of 
the  successive  days,  each  of  these  being  marked  with  the 
number  of  the  day  in  the  course,  and  the  date  on  which 
the  work  is  to  be  done ;  vertical  lines  enclose  spaces  headed 
by  the  two  desk  numbers  of  the  pair  of  students  who  work 
together.  The  numbers  of  the  experiments  are  marked  on 
colored  cards  in  these  spaces.  Reference  to  the  board  will 
show  on  what  day  each  of  the  experiments  is  to  be  per- 
formed. The  colors  of  the  cards  correspond  to  the  colors 
of  the  cards  placed  at  the  top  of  the  board,  giving  the 
names  of  the  instructors,  and  show  to  whom  the  notes  and 
records  of  the  experiments  are  to  be  given. 

METHOD    OF    WORK 

Each  student  is  expected  to  perform  each  experiment, 
and  to  make  out  a  full  report  of  the  results,  accompanied 
by  graphic  records  which  he  himself  has  obtained,  when 
such  were  demanded  by  the  experiment.  He  must  be  pre- 
pared to  be  quizzed  on  the  experiment  at  the  time  it  is 
made,  and  to  pass  an  examination  both  on  the  methods  em- 
ployed and  the  result  obtained,  at  the  end  of  the  course. 
Before  leaving  the  laboratory,  the  student  must  see  that 
his  desk  is  clean  and  neat ;  that  all  apparatus  is  dry  ;  that 
the  battery  has  been  disconnected  fit  is  not  enough  to  leave 
the  key  open)  ;  that  all  apparatus  is  covered.  Care  must 
be  taken  not  to  injure  stools  or  desks.  Of  course  any 
apparatus  which  is  injured  by  a  student  must  be  replaced 
or  paid  for. 


Do  not  begin  an  experiment  until  \<ou  hare  read  the 
directions  in  the  notes,  and  have  clearly  in  mind  the  object 
of  the  experiment. 


EXPERIMENT  1. 


Extensibility  and  Elasticity  of  a  Steel  Spring. 


Apparatus. — The  structure  of  the  drum  kymograph, 
the  method  of  fastening  the  paper  on  the  drum,  of  blacken- 
ing the  paper,  and  of  fixing  the  record,  will  be  explained 
by  the  instructor. 

Examine  your  kymograph  with  care  and  be  sure  that 
you  imderstand  how  the  clockwork  is  wound  up ;  how  to 
change  the  gearing  so  as  to  obtain  the  faster  and  slower 
speeds  of  the  drum ;  how  to  arrange  drum  to  be  driven  by 
the  clockwork  or  to  be  rotated  by  hand ;  and  how  to  raise 
and  lower  the  drum.  The  instrument  will  be  in  order  when 
you  receive  it  and  must  be  in  order  when  you  return  it. 

Mount  spring  with  pointer  (E) 
and  heavier  muscle  lever  (B)   on 
^_U_^^  the  longer   iron  stand,   with   sup- 

porting screw (C) down,  as  shown 
in  diagram.  The  stand  holding 
the  recording  instruments  should 
alwa3^s  be  placed  to  the  right  of 
the  kymograph,  so  that  these  in- 
struments shall  point  in  the  direc- 
tion that  the  drum  revolves.  The 
clockwork  turns  the  drum  clock- 
wise, and  when  it  is  turned  by 
hand  it  should  be  rotated  always 
in  this  direction.  If  the  drum  be 
rotated  backward,  the  recording 
points  are  liable  to  be  injured.  All  records  should  read  from 
left  to  right.  Decide  at  what  part  of  the  drum  the  record 
is  to  be  made  before  finally  clamping  the  recording  appa- 
ratus on  the  stand.  Fasten  two  pieces  of  thread  to  the  writ- 
ing lever  at  the  hole  second  from  the  axis,  and  attach  one  of 


Fig.  I.  Apparatus  for  re- 
cording extensibility  and  elas- 
ticity of  a  steel  spring.  A, 
joint  of  paper  on  drum ;  B, 
lever  ;  C,  supporting  screw  ;  D, 
pin  hook  for  weight ;  E,  steel 
spring;    F,   F,   clamps. 


2  EXPERIMENT   I. 

the  threads  to  the  spring  8  cm.  from  brass  supporting  rod, 
and  the  other  to  a  pin  hook  as  shown  in  diagram.  Observe 
the  following  cautions : 

I. — See  that  the  axis  of  the  writing  lever  is  horizontal. 

2. — See  that  the  thread  connecting  the  lever  with  the 
spring  is  vertical. 

3. — See  that  the  knots  are  securely  fastened. 

4. — See  that  every  clamp  is  screwed  firmly  in  place. 

Now  remove  the  drum  from  the  kymograph,  fasten  a 
sheet  of  glazed  "curve  paper"  smoothly  around  the  drum, 
and  blacken  the  surface  evenly  over  the  gas  flame,  rotating 
the  drum  constantly  so  as  not  to  burn  the  paper.  Replace 
the  drum,  place  the  kymograph  so  that  the  writing  lever 
is  tangent  to  drum  surface,  touching  lightly.  Notice  that 
iever  writes  an  arc  on  a  curved  surface.  If  barely  touching 
when  horizontal,  it  will  leave  the  surface  and  fail  to  write 
as  it  moves  up  or  down.  The  lever  should  press  on  the 
drum  just  enough  to  write  for  2  or  3  cm.  above  and  below 
the  horizontal  line  falling  through  its  axis.  The  position 
of  the  point  with  reference  to  drum  and  joint  of  paper  (A) 
is  indicated  in  the  diagram. 

Experiment. — Turn  the  drum  by  hand  in  a  clockwise 
direction  to  draw  a  base  line  8-10  cm.  long.  Turn  it  back 
(taking  care  not  to  injure  writing  points)  to  the  starting 
point  and  mark  the  place  by  touching  the  lever  lightly.  Now 
turn  drum  clockwise  Yi  cm.  and  then  carefully  place  a  10 
gram  weight  on  the  pin  hook.  Turn  same  distance  again  and 
add  another  weight.  Continue  in  this  manner  until  9  weights 
have  been  added,  then  turn  the  drum  J^  cm.  once  more. 
The  writing  point  has  now  recorded  the  curve  of  extensi- 
bility of  the  spring.  To  obtain  curve  of  elasticity,  turn 
drum  Yz  cm.  in  same  direction  and  remove  one  weight,  and 
continue  in  this  manner  until  .all  the  weights  are  off,  then 
turn  Y^  cm.  once  more,  and  mark  point  by  touching  lever. 

The  vertical  distances  recorded  on  the  drum  should  be  of 
equal  length.  If  they  are  not,  try  to  account  for  the  error. 
Since  steel  is  perfectly  elastic,  the  writing  point  should 
return  to  the  base  line.  If  it  does  not,  try  to  account  for  the 
difference. 


KLASTICITY  OV   STEEf,   SPRING. 


MOUNTING    OF    CUUVKS. 


Using  the  two  triangles  and  a  needle,  or  other  instrument 
with  a  sharp  point,  draw  a  rectangle  about  each  record 
worth  preservation.  It  is  desirable  to  leave  a  generous  mar- 
gin about  the  curve.  Cut  out  piece  thus  outlined,  and  mount 
on  the  cardboard  by  gluing  the  corners  on  with  a  little 
paste.  If  a  knife  be  used  to  cut  off  the  piece,  cut  upon  a 
piece  of  cardboard.  Do  not  cut  on  the  table.  To  protect 
the  curves,  place  over  them  the  sheet  of  paper  upon  Avhich 
the  notes  concerning  the  experiment  have  been  written. 
Let  the  right  hand  end  of  the  sheet  overlap  the  cardboard 
slightly,  and  fasten  it  to  the  back  of  the  cardboard  with 
paste.    Do  not  write  on  cover  paper  when  it  is  over  a  curve. 

THE  student's  notes. 

Write  as  plainly  as  possible  on  the  upper  left  hand  corner 
of  the  paper  which  covers  the  curves,  your  name  and  desk 
number,  and  the  number  of  each  of  the  experiments  mount- 
ed on  the  card.  Also  head  each  mounted  curve  with  the 
number  of  the  experiment  and  the  letter  of  the  subheading 
to  which  it  belongs,  and  label  the  corresponding  notes  on  the 
cover  paper  in  like  manner. 

The  notes  should  contain  an  accurate  statement,  not  of 
what  the  books  say  on  the  subject,  but  of  the  results  act- 
ually obtained  by  you  in  performing  the  experiment.  Do 
not  describe  the  method  of  the  experiment  unless  it  is 
different  from  the  directions  in  these  notes,  in  which  case 
let  the  explanation  contain  all  the  facts  required  to  let 
another  understand  the  exact  conditions  of  the  work.  Men- 
tion all  sources  of  error  which  are  likely  to  arise  from  the 
•method  used.  This  is  most  important.  An  apparatus  is 
a  servant  employed  to  make  observations.  You  must  know 
in  what  respects  its  report  is  to  be  trusted  and  where  it  is 
liable  to  deceive.  It  is  worse  than  useless  to  employ  appar- 
atus in  experiments  or  in  physical  examinations  unless  you 
know  your  apparatus  thoroughly.  If  the  results  obtained 
differ  from  those  v^^hich  you  know  to  be  usually  obtained  in 
similar   cases,    try   to    explain    why    the    difference    occurs. 


4  EXPERIMENT    I. 

Look  upon  each  experiment  as  a  piece  of  original  research, 
and  do  not  be  satisfied  with  simply  carrying  out  directions. 
Learn  to  cultivate  the  power  of  independent  observation 
and  thought.  You  will  be  judged  as  much  by  the  original- 
ity displayed  in  your  reports  as  by  the  accuracy  of  your 
work.  If  you  can  learn  to  observe  accurately  and  to  record 
your  observations  concisely  and  at  the  same  time  in  suffi- 
cient detail  to  make  another  understand  the  results  of  your 
experiments,  you  will  be  able  to  make  a  valuable  physical 
examination  and  keep  a  reliable  case  book. 


lil.ASTlClTY  OF  STEEI,  SPRING. 


KXPERIMENT   I. 


ELASTICITY  01-   FROG'S  MUSCI.E-  7 

EXPERIMENT  II. 
Extensibility  and  Elasticity  of  Frog's  Muscle. 

Apparatus. — Mount  moist  chamber  on  standard,  and 
fasten  threads  to  lever  so  that  it  will  magnify  the  movement 
6  times.  Have  all  apparatus  in  readiness  and  the  drum 
blackened  before  preparing  the  muscle. 

METHOD   OF   KILTING   FROG. 

Kill  a  frog  under  the  direction  of  a  demonstrator. 
Straighten  hind  legs  by  letting  hand  glide  over  body,  and 
wrap  legs  in  dry  cloth.  Insert  one  blade  of  strong  scissors 
into  mouth  as  far  back  as  angles  of  jaw,  and  with  the  other 
blade  across  the  head  as  far  back  as  possible,  remove  skull 
by  a  single  cut  of  the  scissors.  The  cut  should  fall  at  the  back 
of  the  tympanic  membranes,  (See  E,  Fig.  9).  In  making 
the  cut,  hold  frog,  head  down,  over  a  plate.  Cut  off  hind 
legs  close  to  body.  As  there  is  a  possibility  that  the  brain 
may  recover  from  the  shock,  complete  its  destruction  by 
thrusting  a  blade  of  the  scissors  into-  the  cranial  cavity  and 
breaking  up  the  brain.  There  is  no  evidence  that  the  rest 
of  the  nervous  system  is  capable  of  feeling;  nevertheless,  as 
a  matter  of  precaution,  destroy  the  spinal  cord  and  all 
remnants  of  the  brain  with  a  pithing  needle.  Be  sure  that 
all  of  the  central  nervous  system  has  been  destroyed,  for 
even  comparatively  small  parts  in  cold-blooded  animals 
can  recover  from  severe  shock. 

muscle  preparation. 

Remove  the  skin  from  the  leg,  and  put  leg  on  piece  of 
filter  paper  moistened  with  physiological  salt  solution.  Clean 
ofif  the  thigh  muscles  from  femur  without  injuring  tendon  of 
the  gastrocnemius  muscle.  Cut  tendo-Achillis  below  ankle 
and  separate  gastrocnemius  from  tibia.    Remember  that  you 


i\;xpe;riment  II. 


are  not  in  the  dissecting-  room,  and  that  you  are  deahng-  with 
living  tissues.  Do  not  touch  the  muscle  with  the  fingers, 
nor  pinch  it,  nor  injure  it  by  pulling  on  it,  etc.  It  can  be 
handled  by  holding  the  tendon  with  forceps.  Cut  off  tibia 
just  below  knee,  insert  and  fasten  femur  in  clamp  in  moist 
chamber,  put  pin  hook  through  middle  of  tendo-Achillis, 
and  in  doing  this  avoid  pulling  on  muscle.  Place  a  piece 
of  wet  filter  paper  in  the  moist  chamber. 

a.  ExPF,RiMi:N'r. — Repeat  the  work  of  Experiment  i, 
allowing  an  interval  of  ten  seconds  between  the  addition 
or  removal  of  any  two  weights.  The  drum  should  be  moved 
at  the  end  of  lo  seconds,  in  order  that  any  delayed  efifect 
of  the  change  in  load  may  be  recorded  in  the  proper  place. 

After  removing  last  weight  and 
waiting  lo  seconds,  if  the  writing 
point  has  not  returned  to  the 
base  line,  turn  drum  again  and 
wait  one  minute,  repeat  until  lev- 
er ceases  to  rise  or  base  line  is 
reached.  Plot  the  curves  of  ex- 
tensibility and  elasticity  of  mus- 
cle. If  several  curves  are  taken 
with  the  same  muscle,  keep  them 
all  and  label  i,  2,  3,  etc.  Explain 
in  your  notes  the  differences  ob- 
served. 

b.  Plotting  of  Curves. — 
The  curves  drawn  by  the  writing  point  are  inexact  in  two 
respects :  the  point  does  not  move  in  a  vertical  line,  and 
the  drum  may  not  be  moved  equal  distances.  To  obtain 
exact  curves  of  the  extensibility  and  elasticity,  proceed  as 
follows.  Take  a  piece  of  cross  section  paper  and  draw 
heavy  lines  for  the  two  axes.  Mark  dots  at  equal  distances 
along  the  horizontal  axis  (the  abscissa)  and  number  them 
0-10-20,  etc.,  to  represent  the  weights  used,  writing  grams 
at  end  of  line.  Place  along  the  vertical  axis  (the  ordinate) 
at  equal  distances  the  numbers  0-5-10-20,  etc.,  to  represent 
the  number  of  millimeters  through  which  the  writing  point 
moved,  writine  mm,  at  the  head  of  the  column.     As  the 


Fig.  2.  Apparatus  for  record- 
ing extensibility  and  elasticity 
of  frog's  muscle.  A,  moist 
chamber ;  B,  femur  fastened  in 
bone    clamp ;    C,    muscle. 


ELASTICITY  OF  FROG  S  MUSCLEJ.  9 

separate  movements  are  small,  it  may  be  wise  to  let  each 
millimeter  of  movement  be  represented  by  2  or  5  millimeters 
of  the  paper.  Measure  with  the  aid  of  a  magnifying  glass, 
and  the  millimeter  rule  the  exact  height  of  each  movement 
recorded.  It  is  usually  best  to  make  the  measurements  all 
from  the  base  line.  The  amount  of  the  individual  move- 
ments can  be  obtained  by  subtraction.  Give  these  measure- 
ments in  your  notes,  in  order  that  they  may  be  checked, 
and  enter  the  results  on  the  chart,  by  marking,  for  each 
observation,  a  dot  at  the  point  of  intersection  of  the  vertical 
line  •  corresponding  to  the  weight,  and  the  horizontal  line 
corresponding  to  the  height  of  lift.  Now  surround  each  dot 
by  a  little  circle  and  connect  the  circles  by  straight  lines. 
Mount  the  plotted  cun^e  at  the  side  of  the  original.  How 
does  extensibility  differ  from  elasticity?  How  do  the  curves 
obtained  from  muscle  difi'er  from  those  obtained  from  a 
steel  spring?  How  do  the  successive  curves  of  elasticity 
obtained  from  the  same  muscle  differ?     Explain. 


IC  EXPERIMENT    II. 


ELASTICITY  OF  FROG's  MUSCLK.  II 


J 2  KXPERIMKNT   II. 


KHSPONSE  OF  MUSCLE  TO  INDUCTION   SHOCKS. 


EXPERIMENT  Til. 

Response  of  Muscle  to  Making  and  Breaking  Induction 

Shocks  of  Various  Strengths  and  Use  of 

Short  Circuit  Key. 

Apparatus. — Before  preparing  the  muscle,  arrange 
apparatus  as  indicated  in  the  diagram,  mounting  the  moist 
chamber  and  lever  on  the  tall  stand.  Employ  the  light 
muscle  lever  in  this  experiment.  When  the  weight  is  sup- 
ported so  as  not  to  bring  a  strain  on  the  muscle  until  it 


T^i^ 


Fig.  3.  Apparatus  for  recording  contractions  of  frog's  rnuscle,  excited  by  in- 
duction shocks.  A,  pin  electrode ;  B,  primary  coil ;  C,  C,  posts  i  and  2  ;  D,  dry 
cell ;  F,  mercury  key ;  F,  secondary  coil ;  G,  short-circuiting  key ;  H,  light 
muscle  lever;  I,  yoke  of  lever  arranged  to  support  it;  J,  scheme  of  mercury  key 
in  primary  circuit. 

contracts,  we  have  what  is  known  as  an  '"after-loaded  con- 
traction." In  this  case  the  muscle  is  to  be  after-loaded. 
Connect  the  muscle  with  the  sixth  hole  of  the  lever;  see 
that  the  thread  is  vertical ;  rotate  the  yoke  carrying  the  axis 
of  the  lever,  until  it  supports  the  lever  when  the  thread  is 
tense,  and  tighten  the  screw  that  fastens  the  yoke  to  the 
rod.     Xow  suspend  ten  grams   from  the  lever.  To  obtain 


14  DXPERIMUNT  III. 

good  results  it  is  necessary  to  observe  the  following  direc- 
tions : 

I, — Clamp  mercury  key  to  edge  of  table. 

2. — Clean  and  brighten  all  wires  at  points  of  metallic 
contact. 

3. — Connect  wires  of  battery  circuit  (the  primary  cir- 
cuit) to  posts  I  and  2  of  induction  apparatus. 

4. — Turn  binding  screws  firmly  down. 

5. — Leave  key  in  battery  circuit  open  when  not  in  use, 
to  prevent  waste  of  battery. 

6.— See  that  surface  of  mercury  in  key  is  bright,  and 
that  platinum  loop  touches  mercury  in  both  cups  when  key 
is  closed. 

7. — Avoid  closing  key  so  forcibly  as  to  jar  mercury 
globules. 

8. — See  that  thread  is  tense  when  lever  is  properly  sup- 
ported. 

9. — When  it  is  not  the  intention  to  stimulate  the  muscle, 
see  that  short-circuiting  key  is  closed,  to  guard  muscle 
against  accidental  closure  of  primary  circuit. 

Some  Facts  Regarding  Induction  Apparatus. 

Recall  the  following  facts  concerning  the  induction 
apparatus.  The  wire  of  the  primary  coil,  through  which 
the  battery  current  flows,  has  no  metallic  connection  with 
the  \vire  of  the  secondary  coil,  and  consecjuently  the  battery 
current  does  not  enter  the  secondary  coil.  The  current 
which  is  used  to  excite  the  muscles  is  an  induced  current  of 
very  brief  duration,  which  develops  in  the  secondary  coil 
at  the  instant  that  the  battery  current  is  thrown  into,  or  is 
withdrawn  from  the  primary'  coil.  It  is  the  disturbance  of 
the  magnetic  field  about  the  primary  coil,  that  causes  the 
induced  currents  in  the  secondary,  and  the  induced  currents 
are  of  very  brief  duration,  lasting  only  until  equilibrium 
has  been  established.  The  nearer  the  secondary  approaches 
the  primary  coil,  the  more  it  comes  under  the  influence  of 
the  magnetic  field  about  it,  and  the  stronger  the  induced  cur- 
rents become.  Like  movements  of  the  secondary  coil,  result 
in  a  more  and  more  rapid  growth  in  the  intensity  of  the  in- 


RESPONSE  OF   MUSCLE  TO  INDUCTION   SHOCKS.  1 5 

duced  currents  as  the  primary  coil  is  approached ;  a  move- 
ment of  a  milHmeter  when  the  secondary  is  close  to  the  pri- 
mary increases  the  induced  current  as  much  as  a  movement 
of  a  centimeter  or  more  when  the  coils  are  far  apart.  Rota- 
tion of  the  secondary  coil  on  the  pivot,  because  changing  the 
angle  at  which  the  lines  of  magnetic  force  will  cut  the  wind- 
ings, also  influences  the  development  of  the  induced  cur- 
rents, and  they  become  less  the  more  the  angle  between  the 
two  coils  approaches  a  right  angle. 

I'Vhy  is  the  making,  -weaker  than  the  breaking  induction 
shock f  When  the  battery  current  is  made,  an  electro- 
motive force  is. set  up  in  the  primary  coil,  and  this  force 
induces  a  counter  electro-motive  force  in  that  coil  of  oppo- 
site direction  to  that  of  the  battery  current.  As  a  result,  the 
disturbance  in  the  magnetic  field  about  the  primary  coil  is 
slow  to  develop  and  comparatively  slight,  and  the  making 
induced  current  in  the  secondary  coil  gains  its  full  intensity 
slowly  and  is  feeble.  AV'hen  the  battery  current  is  broken, 
the  electro-motive  force  induced  in  the  primary  coil  has  the 
same  direction  as  that  of  the  battery  current,  and  conse- 
quently the  breaking  induced  current  in  the  secondary  coil 
gains  its  full  intensity  very  rapidly  and  is  very  strong. 

a.     Response  to  Making  and  Breaking  Shocks  of  Increas- 
ing Strength. 

Experiment. — Place  muscle  preparation  in  the  moist 
chamber,  insert  pin  electrode  into  the  tendo-Achillis  (not 
the  muscle  substance).  The  exciting  current  will  pass 
through  muscle  from  end  to  end.  Place  kymograph  so  that 
lever  bears  lightly  on  drum  near  the  joint  of  the  paper. 
Move  secondary  coil  as  far  from  primary  as  the  construction 
of  instrument  permits,  then  turn  it  on  the  pivot  until  it  is  at 
right  angles  to  the  primary  coil.  Now  open  short  circuit 
key  and  make  and  break  the  primary  circuit  by  means  of 
the  mercury  key :  no  contraction.  The  stimulus  is  sub-mini- 
mal. Gradually  turn  the  coil  to  strengthen  the  induced  cur- 
rent, making  and  breaking  the  circuit  at  each  new  position 
of  coil.  A  position  will  be  found,  either  while  turning  the 
coil   or   afterwards   by   sliding   it   towards   the   primary,   at 


l6  KXPEKIMENT  III. 

which  a  small  contraction  will  result.  Notice  that  the  con- 
traction occurs  on  breaking  the  circuit  and  that  no  cor- 
responding making  contraction  is  seen.  Now  give  muscle 
a  rest  of  Yz  a  minute  and  then  try  to  put  the  secondary  coil 
in  such  a  position  that  the  contraction  will  be  so  small  as 
to  be  scarcely  visible.  Such  a  contraction  is  said  to  be 
minimal.  These  later  trials  should  be  made  at  intervals  of 
not  less  than  lo  seconds. 

Now  move  the  drum  a  few  centimeters,  and  record  first 
a  minimal  contraction,  and  then,  y^  cm.  apart,  a  series  of 
breaking  contractions  obtained  by  stimulating  with  gradu- 
ally increasing  stimuli.  In  stimulating,  make  the  circuit, 
wait  5  seconds,  then  break,  and  wait  lo  seconds.  If  the 
stimuli  are  given  too  rapidly  the  irritability  of  the  muscle 
will  be  raised.  Soon  a  contraction  will  appear  when  the 
circuit  is  made,  but  smaller  than  the  breaking  contraction 
that  goes  with  it.  If  the  secondar}^  coil  has  not  been  moved 
too  rapidly  this  first  making  contraction  will  be  nearly  mini- 
mal. After  a  minimal  making  contraction  has  been  obtained, 
continue  stimulating  and  recording  as  before.  After  a  time 
the  breaking  and  making  contractions  will  be  maximal,  i.  e., 
will  cease  to  grow  with  increasing  strength  of  current,  and 
if  the  work  is  continued,  a  second  growth  in  height  of  con- 
tractions may  be  seen,  and  supra-maximal  contractions 
be  recorded.  Mark  on  the  record  to  indicate  which  con- 
traction is  a  minimal  break,  a  minimal  make,  a  maximal 
break  and  a  maximal  make. 

h.     Use  of  Short  Circuit  Key. 

Move  drum  a  few  centimeters,  then  slide  secondary  coil 
to  a  position  which  excites  making  contractions  about  half 
as  high  as  the  corresponding  breaks,  and  record  four  mak- 
ing and  four  breaking  contractions,  stimulating  with  same 
time  intervals  as  in  part  a,  but  with  the  strength  of  current 
unchanged.  Move  drum  a  short  distance,  close  the  short  cir- 
cuit key  and  stimulate  :  no  contraction.  Two  paths  are  now 
open  to  the  current,  and  the  current  is  divided  between  them 
in  inverse  proportion  to  the  resistances.     The  muscle,  hav- 


RESPONSE  OE*  MUSCLE  TO  INDUCTION   SHOCKS.  1 7 

ing  much  greater  resistance  than  the  metal  of  the  short 
circuit  key,  gets  so  little  current  that  the  stimulus  is  sub- 
minimal. This  method  of  dividing  the  current  is  technically 
known  as  "shunting." 

Leaving  coil  in  same  position,  record  a  series  of  four 
making  contractions,  cutting  out  breaks  with  short  circuit 
key,  then  record  a  series  of  four  breaks,  cutting  out  the 
makes  in  the  same  manner.  Indicate  which  are  makes  and 
which  are  breaks  in  the  last  group  of  records. 


EXPERIMENT  III. 


RESPONSE  OF  MUSCJ^F,  TO  INDUCTION   SHOCKS.  19 


20 


IJlXPERIMENT  III. 


CURVE  OF  WORK. 


EXPERIMEXT  IV. 

Relation  of  Amount  of  Load  to  Height  of  Lift  and 
Quantity  of  Work  Done. 

Apparatus. — The  same  apparatus  is  to  be  employed  as 
in  Experiment  3,  except  that  the  heavy  muscle  lever  is  to 
be  used.  Because  of  the  heavy  load  to  be  carried,  care  must 
be  taken  to  fasten  securely  all  clamps,  threads,  and  hooks. 
The  muscle  is  to  be  after-loaded,  and  the  supporting  screw 
must  be  carefully  adjusted  so  that  the  whole  height  of  each 
contraction  shall  be  recorded.  Make  note  of  the  amount  of 
magnification.     Have  20  ten-gram  v/eights  readv  for  use. 

a.  Experiment. — Place  muscle  in  moist  chamber,  and 
make  electrical  connections  as  in  Experiment  3.  Find 
strength  of  current  required  to  produce  maximal  breaking 

contractions  of  unloaded  mus- 
cle. In  doing  this  avoid  fa- 
tiguing muscle  by  too  frequent 
excitations.  For  stimuli  use 
maxim.al  breaks  at  intervals  of 
15  seconds,  and  cut  out  the 
makes  with  short-circuiting 
key.  Record  on  the  drum  at 
distances  of  j^  cm.,  the  con- 
tractions obtained  with  o,  10, 
20,  30,  etc.  grams,  and  contin- 
ue the  addition  of  weights  un- 

Fig.    4.       Curve    of    lift    and    of  .,       ,  ,  , 

work.      A,  curve  of  lift;   B,  curve  tli    the    mUSClC    Cau    UO    lougcr 

°^  ^°^^-  lift    the    load.      The    muscle 

should  be  able  to  life  70  grammes.  If  more  than  one  ex- 
periment is  made  with  the  same  muscle,  state  the  fact,  since 
fatigue  will  modify  the  results.  The  "absolute  power"  of 
the  muscle  is  measured  by  the  weight  which  the  muscle 
just  fails  to  lift  and  which  cannot  stretch  it  when  contract- 
ing. 


30 

\ 

so 
10 
0 

^'\ 

A. 

\^ 

\"  '• 

/gems 

200 

too 

\ 

\ 

./ 
/ 

6(IQ 

B 

22        .  EXPERIMENT  IV. 

b.     Plotting  of  Curves. 

State  in  tabular  f omi  on  the  cardboard,  by  the  side  of 
the  original  curve,  the  recorded  height  of  lift,  and  the  ap- 
parent work  done  by  each  of  the  contractions,  (the  work 
being  the  product  of  the  height  times  the  weight  lifted), 
and  the  actual  work,  which  is  obtained  by  dividing  the 
figures  of  the  apparent  work  by  the  magnification  of  the 
lever. 

To  plot  the  curves  of  lift  and  work,  take  a  piece  of  cross- 
section  paper,  about  lo  cm.  square,  and  lay  off  axes  as 
shown  in  diagram.  Plot  above  the  abscissa  line  the  curve  of 
lift,  showing  the  heights  of  the  contractions, — the  ordinates 
representing  the  distances  through  which  the  weight  was 
moved  and  the  abscissas  the  weights.  Plot  below  the  ab- 
scissa line  the  curvT  of  work,  the  ordinates  representing  the 
work  and  the  abscissas  the  weights.  In  plotting  the  curves, 
I  mm.  of  cross  section  paper  can  be  used  to  represent  any 
desired  value  of  the  curve  to  be  plotted.  The  curve  can 
magnify  or  reduce  the  values  actually  obtained.  For  ex- 
ample. I,  2,  or  3  mm.  on  the  cross-section  paper  can  stand 
for  I  mm.  of  lift,  and  5,  10  or  20  mm.  on  the  paper  can 
represent  100  grammillimeters.  Be  sure  to  state  on  the 
plotted  curve  the  values  of  ordinates  and  abscissas,  as  shown 
in  Fig.  4. 

With  what  weight  was  the  greatest  amount  of  work 
done?  What  was  the  actual  amount  of  work  done  with 
this  weight?  What  was  the  "absolute  power"  of  the  muscle? 
Have  the  results  any  practical  bearing? 


cuRvn;  OF  work. 


23 


24  EXPERIMENT  IV. 


FATIGUE  OF   HUMAN    MUSCLE.  25 

EXPERIMENT  V. 

Fatigue  of  Human  Muscle. 

Apparatus. — Many  interesting  facts  concerning  the 
fatigue  of  human  muscle  and  the  conditions  on  which  it 
depends  have  been  ascertained  by  the  use  of  the  ergograph. 
The  effects  of  fatigue  have  been  studied  by  i,  letting  the 
muscle  bend  a  stiff  spring,  the  movement  of  which  is  greatly 
magnified,  i.  e.,  by  the  isometric  method;  2,  by  letting  the 
muscle  raise  a  weight,  i.  e.,  the  isotonic  method.  Several 
forms  of  apparatus  are  in  use  in  the  laboratory,  and  each 
is  accompanied  by  directions.  In  the  following  experiments 
the  isotonic  method  will  be  used.  Apparatus  for  the  iso- 
metric method  will  be  provided  if  desired. 

Experiment. — Connect  a  time  signal  with  the  clock 
circuit  and  adjust  it  to  write  below  the  writing  point  of  the 
ergograph.  Be  careful  that  the  hand  is  securely  fixed,  so 
that  the  work  shall  be  done  only  with  the  group  of  muscles 
which  are  supposed  to  be  used,  and  that  it  is  comfortable, 
so  that  painful  sensations  shall  not  interfere  with  the  work. 
Throughout  the  work,  watch  the  metronome,  and  raise  the 
weight  and  lower  the  weight  rhythmically,  taking  care  to 
maintain  the  rhythm.  Always  try  to  raise  the  weight  as 
much  as  possible.  Unless  a  maximum  effort  is  made  each 
time,  the  experiment  is  worthless.  If  the  abductor  of  the 
index  finger  is  to  be  used,  a  weight  of  500  to  1,000  grams 
may  be  employed,  the  amount  varying  with  the  strength  of 
the  individual  and  the  apparatus.  In  case  the  flexors  of  the 
second  finger  (the  sublimis,  profundus,  and  lumbricales) 
are  to  be  used,  two  to  four  kilos  can  be  employed. 

a.     Effect  of  Sloiv  Rate. 

The  muscles  are  to  contract  at  the  rate  of  once  in 
two  seconds.  Adjust  the  metronome  for  the  required 
rhythm,    and    see    that    it    is    wound    up.      Arrange    the 


26  EXPERIMEJNT  V. 

drum  to  run  at  the  rate  of  2  mm.  per  second.  Start 
metronome ;  raise  weight  while  the  metronome  pointer 
swings  in  one  direction,  and  lower  it  quickly  when  it  swings 
back.  Make  a  few  contractions  to  catch  the  rhythm ;  rest 
a  minute ;  then,  being  careful  to  maintain  the  rhythm 
throughout,  and  ahvays  raising  the  weight  as  high  as  pos- 
sible, record  the  contractions  for  two  minutes. 

b.  Bifect  of  Quick  Rate. 

Rest  3  minutes.  Adjust  metronome  to  beat  seconds, 
then  repeat  the  work,  raising  the  weight  during  one-half 
second  and  lowering  it  quickly.  Work  until  the  weight  can 
not  be  raised. 

c.  Effect  of  Rest. 

Rest  3  minutes  and  repeat  work. 

d.  Effect  of  Massage. 

Rest  3  minutes,  and  during  the  rest,  massage  the  muscles 
vigorously.    Repeat  the  work. 

In  your  notes  state  the  length  of  time  during  which  the 
weight  could  be  raised  and  the  character  of  the  fatigue 
curve,- — i.  e.,  the  way  in  which  the  height  of  contractions 
altered.  The  amount  of  work  could  be  estimated  if  desired 
by  adding  the  height  of  the  separate  contractions  and  multi- 
plying by  the  weight  lifted.     Explain  results. 


IfATIGUr;  OF  HUMAN   MUSCLl];.  27 


EXPERIMENT  V. 


TIME  RFXATIONS  OF  MYOGRAM.  29 


expf:riment  vl 

Time  Relations  of  Myogram. 

The  record  of  a  sing'le  muscle  contraction  is  called  a 
myogram.  Hitherto  we  have  been  concerned  onl)^  with 
the  height  of  the  myogram,  which  can  be  best  observed 
when  recorded  on  a  stationary  drum.  In  order  to  study  the 
time  relations  of  the  myogram,  the  record  will  have  to  be 
taken  on  a  moving  drum,  and  the  rate  of  movement  of  the 
drum  be  detennined  with  a  tuning  fork. 

a.     Influence  of  Rate  of  Drum  on  Form  of  Myogram. 

There  are  today  a  great  variety  of  methods  for  obtain- 
ing graphic  records  of  physiological  processes  and  the 
changes  which  they  undergo  under  normal  and  pathological 
conditions.  In  many  cases  these  records  are  taken  on  mov- 
ing surfaces,  and  it  is  important  that  one  should  be  able  to 
estimate  the  influence  of  the  rate  of  motion  of  the  surface 
on  the  shape  of  the  curve.  ; 

Apparatus. — The  apparatus  for  supporting  the  muscle"^ 
and  recording  its  contraction,  and  the  electrical  connections 

with  the  induction  coil  are 
to  be  the  same  in  this,  as  in 
Experiment  3,  the  lighter 
muscle  lever  being  used.  In 
this  experiment,  however,  the 
key  in  the  primary  circuit,  in- 
stead of  being  opened  by 
hand,  is  to  be  opened  auto- 
matically by  the  drum  when  it 
is  revolved.  That  this  may 
be  done,  fasten  a  frog  board 

Fig.  s.     Apparatus  for  automatically  ^y    its    irOU    rod    tO    clamp    On 

exciting   muscle    by   letting   the    drum  cf,ot-t      stanri  Plarf-      tpv      in 

open  the  key.     A,  frog  board ;  B,  cabi-  ^    "    ^      SiaUQ.        ±  laCC      Key      m 

net   maker's   clamp;    C,   mercury  key;  primarv    cirCUit    OU    the   board, 
U,    handle    of    key;    E,    key    opener;  ,      '     .  . 

F,  wires  to  primary  circuit ;  G,  tuning  SO     that     it     prOJCCtS     for    tWO- 

""^  '     '  ^°  ^"  thirds  of  its  length  beyond  it. 

and  clamp  key  to  board  by  a  cabinetmaker's  clamp.  Adjust 


G 


30  EXPERIMENT  VI. 

board  so  that  top  of  key  is  just  above  the  level  of  the  top 
oi  the  drum.  Clamp  the  key  opener  to  the  top  of  the  drum, 
so  that  it  projects  a  couple  of  cm.  beyond  it.  Now  move 
the  key  just  near  enough  to  enable  the  key  opener  to  open  it. 

Experiment. — Blacken  a  drum ;  bring  key  into  position 
to  be  opened  w^hen  drum  is  turned ;  leave  key  open  when 
the  current  is  not  wanted. 

Prepare  a  gastrocnemius  muscle;  suspend  it  in  moist 
chamber  and  connect  it  with  lever;  thrust  pin  of  pin  elec- 
trode through  tendon;  adjust  support  so  that  muscle  shall 
be  after-loaded  zvhen  thread  is  tense  and  the  lever  is  hor- 
izontal. Let  short-circuiting  key  be  closed  when  it  is  not 
desired  to  excite  muscle;  place  secondary  coil  so  that 
muscle  shall  give  a  maximal  breaking  contraction ;  short 
circuit  all  making .  shocks ;  rotate  drum  so  that  the  part 
which  opens  key  wall  point  away  from  it.  Now  place  stand 
so  that  the  lever  will  write  well  upon  the  drum.  Close  key 
in  primar}'  circuit  and  then  open  short-circuiting  key.  Now 
open  key  in  primary  circuit  by  rotating  drum  by  hand  very 
slo7i'ly.  A  breaking  contraction  will  be  recorded.  Do  not 
move  the  kymograph,  or  the  stands  holding  key  and  lever. 
Repeat  the  experiment  four  times,  each  time  rotating  the 
drum  somewhat  faster.  Fix  the  record.  State  in  notes  in 
what  respects  the  myograms  obtained  differ.  Save  the 
muscle  to  test  the  apparatus  in  part  h. 

h.     Time  Relations  of  Myogram. 

Apparatus. — Use  the  same  apparatus  as  in  a,  with  the 
following  additions :  Mount  on  long  stand  beneath  the 
muscle  lever  a  tuning  fork,  to  mark  rate  of  movement  of 
drum.  Put  on  the  wire  spring,  used  in  Experiment  I,  a 
celluloid  pointer,  and  clamp  the  spring  beneath  the  fork,  to 
give  a  base  line  to  be  used  in  measuring  the  curves.  See 
that  the  three  writing  points  are  in  the  same  vertical  line, 
using  a  drum-square  for  this  purpose.  Mark  the  position  on 
the  drum  by  moving  each  point.  To  be  sure  that  these 
marks  shall  be  recognized  make  a  little  cross  over  each  of 
them.  Save  the  part  of  the  curve  showing  the  relative  po- 
sition of  the  points. 

This  method  should  be  employed  in  all  experiments  in 
which  time  relations  are  important. 


TIMU  RELATIONS  OP  MYOGRAM.  3I 

ExPERrMENT. — The  latent  period,  the  duration  of  the 
period  of  rise  and  of  the  period  of  fall,  are  all  longer  for 
a  fatigued  than  for  a  fresh  muscle;  it  is  therefore  best  to 
test  apparatus  with  muscle  used  in  part  o.  When  you  have 
learned  to  perform  the  experiment  promptly  prepare  a  fresh 
muscle.  Ascertain  the  current  just  strong  enough  to^  give 
a  maximal  breaking  contraction,  and  in  doing  this  avoid 
exciting  the  muscle  too  often  and  call  out  as  few  con- 
tractions as  possible.  After  the  drum  has  been  blackened, 
and  the  mercury  key  has  been  placed  so  that  it  will  be 
opened  when  the  drum  revolves,  see  that  the  lever  is  hori- 
zontal when  resting  on  its  support  with  thread  tense.  Then 
move  long  stand  so  that  fork  and  muscle  lever  will  write 
lightly  on  drum.  If  now  the  drum  is  revolved,  the  mer- 
cury key  will  be  opened  when  the  muscle  lever  is  at  a  cer- 
tain point  on  the  drum  surface.  To  find  what  this  point  is, 
with  short  circuit  key  closed,  close  mercury  key ;  then  open 
short  circuit  key,  and  open  mercury  key  by  revolving  the 
dnmi  very  slozvly.  The  recorded  myogram  should  be  almost 
a  single  line.  The  contraction  of  the  muscle  v/ill  mark  the 
point  of  drum  which  was  opposite  the  end  of  the  lever 
when  the  muscle  was  stimulated.  Now,  without  changing 
position  of  key,  drum,  or  lever,  close  short  circuit  key, 
revolve  drum  two-thirds  the  way  round,  put  yoke  on  fork, 
close  mercury  key ;  then  pull  yoke  off  of  fork  and  immedi- 
ately open  mercury  key  by  revolving  drum  rapidly.  Stop 
drum  at  the  close  of  one  revolution.  Tf  the  muscle  had 
contracted  immediately  the  second  curve  would  have  begun 
to  rise  at  the  same  point  as  the  first.  It  does  not,  because 
the  muscle  has  a  latent  period.  The  distance  between  the 
beginning  of  the  two  curves  shows  the  length  of  this  period, 
because  the  tuning  fork  curve  enables  us  to  know  how  long 
the  drum  took  to  traverse  this  distance. 

c.     Measurement   of  Records   and   Computation   of   Time 
Intervals. 

To  determine  the  latent  period,  it  is  first  necessary  to  fix 
the  exact  points  at  which  the  two  contractions  began.  Draw 
through  the  point  of  origin  of  the  first  recorded  contraction 
the  line  MM,  perpendicular  to  the  base  line.   To  fix  the  point 


32 


EXPERIMKNT  VI. 


at  which  the  second  contraction  began,  draw  on  the  curve 
two  fine  parallel  lines,  one  just  aboA^e  and  one  just  below 
the  line  traced  by  the  lever,  as  at  AB,  to  aid  the  eye  in  fixing 
the  point.  Draw  through  it  the  line  OP  and  estimate  MO, 
the  latent  period,  in  thousandths  of  a  second.  One  double 
vibration  of  the  fork,  measured  from  the  crest  of  one  vibra- 
tion to  that  of  the  next,  is  one  hundredth  of  a  second.  A 
good  way  of  ascertaining  the  length  of  the  latent  period,  is 
to  estimate  the  value  of  one  millimeter  of  drum  surface  in 
thousandths  of  a  second,  by  dividing  the  time  of  one  double 
vibration  of  the  fork  bv  the  number  of  millimeters  in  the 


Fig.    6.      Method    of   preparins 
termination  of  latent  period. 


myogram    for    de- 


wave  which  is  recorded  most  nearly  between  MO,  and 
multiplying  this  value  by  the  number  of  millimeters  in  the 
recorded  latent  period. 

To  determine  the  period  of  contraction,  draw  TO  per- 
pendicular to  MN  and  tangent  to  the  muscle  curve  at  Q. 
With  a  radius  equal  to  the  length  of  the  writing  lever  and 
a  center  on  the  base  line  traced  by  the  muscle  lever,  as  at 
R,  revolve  to  Q  to  the  base  line  at  S,  draw  the  perpendicular 
UV  through  S,  and  estimate  the  number  of  thousandths 
of  a  second  between  0  U.  To  do  this  count  the  complete 
waves,  and  estimate  in  tenths  the  fractions  of  waves.  The 
line  UV  must  not  be  drawn  through  0,  because  the  distance 
WQ  is  due  to  the  fact  that  the  muscle  lever  draws  an  arc 
instead  of  a  straight  line.  To'  determine  the  period  of  relax- 
ation, draw  XY  through  the  point  where  the  muscle  curve 
strikes  the  base  line  at  A^. 

State  in  notes  length  of  latent  period,  contraction  period, 
and  relaxation  period,  in  tabular  form.  Also  mention  the 
most  likely  sources  of  error. 


TIMF.  RELATIONS  OF  MYOGRAM,  33; 


04  EXPCRIMKNT  VI, 


GENESIS  01"  TETANUS. 


35 


KXPERIMENT  VII. 


Genesis  of  Tetanus. 


Fig.  7.  Apparatus  for  studying  sum- 
mation of  contractions.  A,  block  of 
wood  wound  with  aluminum  wire ; 
B,  primary  coil ;  C,  C,  posts  i  and  2  ; 
D,  dry  cell ;  E,  bare  end  of  insulated 
wire  turned  back  on  itself. 


Apr.ARATus. — The  apparatus  is  to  be  arranged  as  in 
Experiment  3.  except  that  the  mercury  key  is  to  be  omitted, 
and  the  current  of  the  battery  circuit  is  to  be  made  and 

broken  as  folloAvs : 

Fasten  the  block  of 
wood  on  which  the  aluminum 
wire  is  wound,  to  the  edge 
of  the  table  by  a  cabinet- 
maker's clamp.  Connect  the 
binding  post  on  block  with 
post  I  of  coil ;  connect  post 
2  of  coil  with  one  pole  of 
dry  cell;  and  fasten  an  in- 
sulated wire  to  the  other 
pole.  NoAV  bend  the  free 
end  of  this  wire  back  on 
itself,  so  that  the  end  shall  be  smooth  and  rounded.  See 
that  the  wire  is  bright.  If  this  wire  be  touched  to  any  part 
of  the  aluminum  coil  the  primaiy  circuit  will  he  made, 
and  if  the  wire  is  drawn  across  the  coils,  a  series  of  making 
and  breaking  shocks  will  be  given. 

a.     Sinnmation  of  Two  Contractions. 

If  two  stimuli  reach  a  muscle  at  a  sufficiently  short  inter- 
val the  second  contraction  process  may  begin  before  the 
first  one  is  complete.  What  will  be  the  result?  In  this, 
as  in  the  preceding  experiments,  each  student  is  to  do  the 
work  independently. 

Experiment. — Blacken  drum  and  arrange  for  quick 
speed  ;  make  a  muscle  preparation  and  mount  it  in  moist 
chamber,  as  in  Experiment  III ;  place  drum  so  that  lever 


_36  EXPERIMIJNT  VII. 

will  record  well.  Open  short  circuit  key ;  with  the  drum 
still,  excite  the  muscle  by  drawing  free  end  of  wire  con- 
nected with  battery  across  the  last  turn  of  aluminum  wire 
on  block  (Fig.  7,  A)  ;  choose  a  strength  of  induced  current 
which  will  give  a  good  breaking  and  no  making  contraction. 
Let  muscle  rest.  Now  start  drum,  and  draw  wire  across 
windings  a  and  b,  at  such  rate  as  to  cause  two  separate 
contractions ;  repeat  several  times,  and  more  quickly  each 
time,  until  the  two  contractions  look  like  one.  How  do  the 
records  differ? 

b.     Incomplete  Tetanus  and  Complete  Tetanus. 

Apparatus. — Use  the  same  apparatus  as  in  a,  and  in 
addition  mount  a  time  signal  (chronograph)  so  that  the 
writing  point  will  write  below  and  in  same  vertical  line 
with  the  muscle  lever.  Connect  the  signal  with  the  bind- 
ing posts  on  the  side  of  the  desk.  Tn  the  time  circuit,  there 
is  a  battery,  and  a  clock  which  interrupts  the  circuit  once 
a  second.  The  signal  should  record  seconds  on  the  drum. 
The  drum  should  run  4  cm.  per  second. 

Experiment.— Make  experiment  as  in  a,  only  this  time 
draw  wire  across  all  the  windings  of  the  aluminum  coil. 
In  doing  this  see  that  the  hand  is  moved  at  an  even  rate 
across  the  coil.  The  experiment  is  a  test  not  only  of  the 
behavior  of  the  frog's  muscle  under  varying  rates  of  stimuli, 
but  your  capacity  to  move  the  hand  constantly  at  different 
speeds,  i.  e.,  muscle  coordination.  State  in  notes  approxi- 
mately the  numher  of  excitations  per  second  required  to 
tetanise.  Do  not  forget  that  an  arc  must  be  drawn.  A 
complete  tetanus  is  an  apparently  continuous  contraction 
produced  by  a  series  of  excitations.  All  voluntary  contrac- 
tions are  tetani. 

■  c.     Complete  Tetanus  Obtained  zvith  AutomMtic  Interrupter. 

Apparatus. — The  apparatus  is  the  same  as  in  Experi- 
ment III,  excepting  that  the  battery  and  key  are  connected 
with  different  posts  of  the  primary  coil. 


GENESIS  OF  TETANUS. 


37 


Electrical    Connections    m    Primary    Circuit    of    Induction 

Apparatus. 

Two  kinds  of  coils  are  in  use.  Model  A  in  which  the 
secondary  coil  slides  on  metal  rods,  and  Model  B  in  which 
the  secondary'  coil  slides  on  the  wooden  base.  The  way  in 
which  the  binding  posts  belonging-  to  the  primary  circuit 
are  connected  with  the  primary'  coil  and  the  automatic  in- 
terrupter is  different  in  these  two  forms  of  apparatus. 

MODEL   B. 


Fig.  S.  Scheme  of  electrical  connections  of  primary  coil  in  two  forms  of  in- 
duction apparatus.  A,  soft  iron  wires  in  primary  coil;  C,  hammer;  C,  contact 
screw;  i,  2,  3,  binding  posts. 


Model  A — To  obtain  single  making  and  breaking  shocks 
use  posts  I  and  2.  To  obtain  tetanizing  current  use  posts 
I  and  3. 

Model  B — I'o  obtain  single  making  and  breaking  shocks 
use  posts  I  and  2.  To  obtain  tetanizing  current  use  posts  2 
and  3. 

In  each  apparatus  if  single  shocks"  are  needed,  the 
battery  and  key  are  connected  with  the  posts  to  which 
the  two  ends  of  the  wire  of  the  primary'  coil  are  directly 
attached.  If  a  long  series  of  rapidly  following  shocks  are 
needed,  as  for  tetanus,  the  batterv  and  key  have  to  be  so 
connected  as  to  bring  the  automatic  interrupter  into  the  cir- 
cuit. This  is  done  in  Model  A  by  connecting  the  battery 
with  posts  I  and  3.  The  current  can  then  enter  by  post  3, 
pass  to  the  contact  screw,  down  the  spring,  then  through 
the  wire  of  the  primary  coil,  and  away  by  post  i.  In  Model 
B,  posts  2  and  3  are  used.     The  current  enters  by  post  3, 


38  EXPERIMENT  VII. 

passes  to  contact  screw,  down  the  spring,  through  the  coil, 
and  away  by  post  2. 

In  each  case,  as  the  current  flows  through  the  coil  it 
magnetizes  iron  wires  inside  it,  and  the  hammer  is  attracted. 
The  movement  of  the  hammer  breaks  the  contact  between 
the  spring  and  the  contact  screw,  and  the  current  ceases  to 
flow ;  the  soft  iron  wires  lose  their  magnetism,  the  hammer 
is  released,  and  the  spring  again  makes  contact  with  the 
contact-screw.  Thus  the  primary  current  is  being  contin- 
ually made  and  broken,  and  a  series  of  rapidly  following 
induction  shocks  develop  in  the  secondary  coil. 

Notice. — In  order  that  the  automatic  interrupter  may 
work  well,  the  contact-screAv  is  screwed  up  until  it  barely 
touches  the  spring  when  at  rest. 

HxPEKiMENT. — After  the  apparatus  has  been  arranged, 
the  automatic  interrupter  tested,  and  a  fresh  drum  black- 
ened, prepare  a  muscle  and  mount  it  in  the  moist  chamber. 
Now  adjust  lever  to  drum ;  see  that  short-circuiting  key 
is  closed ;  close  key  in  primary  circuit ;  start  kymograph 
clockv/ork  (quick  speed)  ;  open  short-circuit  key  for  a  few 
seconds;  the  close  short-circuit  key;  stop  drum  a  few 
seconds  later  and  open  key  in  primary  circuit.  If  the  curve 
does  not  return  to  the  base  line  promptly  when  the  excita- 
tion ceases,  it  is  because  the  after  contraction,  known  as 
"Contracture,"  is  present. 

d.  Fatigue  Caused  by  Tetanus. 

Experiment. — This  experiment  is  to  be  made  with  the 
same  muscle  and  in  the  same  manner  as  c,  excepting  that  the 
drum  should  revolve  slowly  and  the  tetanic  excitation  be 
permitted  to  act  on  the  muscle  until  it  is  completely  fatigued. 

e.  Fatigue  of  C 011  tinned  Voluntary  Contractions. 

In  the  case  of  voluntary  muscular  contractions  of  the 
arm,  as  the  final  step  of  the  brain  processes  which  result  in 
the  effort,  the  cells  in  the  motor  arm  area,  anterior  to  the 
fissure  of  Rolando,  become  active  and  send  stimuli  to  the 
anterior  horn  cells  in  the  gray  matter  of  the  spinal  cord, 
and  they  discharge  nerve  impulses  at  a  rapid  rhythm,  which 


GENESIS  OF  TETANUS.  39 

cause  the  muscles  to  be  tetanized.  By  continued  voluntary 
contraction  fatigue  shows  itself  in  much  the  same  manner 
as  in  the  above  experiment. 

Test  this  by  raising  the  left  arm  to  the  horizontal  po- 
sition, and  trying  to  hold  it  there.  Gradually  the  arm  tends 
to  fall  and  stronger  efforts  must  be  m.ade  to  bring  it  back 
to,  or  hold  it  in  the  horizontal  position.  As  fatigue  comes 
on.  painful  sensations,  not  at  first  noticed,  come  from  the 
muscle  sense  organs.  It  is  not  necessary  to  carry  the  ex- 
periment to  complete  fatigue.  Describe  the  result  of  your 
experiment.  State  where  the  fatigue  probably  occurred, 
and  vour  reasons. 


40  EXPERIMENT  VII. 


GENUSIS  OI^  TETANUS.  4 1 


42 


1<,XP!'.!^TMF,NT  VII. 


RATE  OF  TAPPING.  43 


EXPERIMENT  VIII. 

Rate  of  Tapping. 

The  apparatus  permits  a  determination  of  the  greatest 
speed  with  which  it  is  possible  to  make  a  series  of  brief 
voluntary  contractions  (tetani)  of  a  muscle. 

Apparatus. — Adjust  a  drum  to  the  pointer  of  a  time 
signal  and  the  recorder  of  the  apparatus,  which  is  held  in 
contact  with  the  surface  by  a  delicate  weighted  thread.  Con- 
nect the  time  signal  to  the  clock,  so  as  to  record  seconds. 
Carefully  pull  the  cross-needle  down  as  far  as  possible.  Place 
the  arm  on  the  board  and  practice  tapping  the  Morse  key, 
being  careful  to  use  a  wrist  movement  only,  and  saving  time 
by  moving  the  hand  through  very  short  distances.  Each  tap 
causes  the  cross-needle,  operated  by  the  clockwork,  to  rise  a 
definite  amount. 

ExPKRiMENT. — With  cross-needle  down,  start  the  drum 
at  a  rate  of  2  mm  per  second  and  begin  tapping;  keeping 
this  up  at  a  steady  rate  till  the  cross-needle  reaches  the 
upper  stop.  Try  this  for  the  right  and  left  hand.  Now 
figure  the  number  of  seconds  required  to  tap  234  times  (the 
number  necessary  to  make  a  complete  rise  of  the  cross- 
needle).  Determine  the  number  of  taps  per  second  for 
•each  hand.  Notice  in  the  record  the  failure  to  tap  when  the 
rate  became  too  rapid.  What  was  the  cause?  Discuss  the 
physiological  value  of  the  experiment. 


44 


expi;rime:.nt  viii. 


RATE  OP  TAPPING.  4^ 


46  EXPERIMENT  VIII. 


INDEPENDENT  IRRITABILITY  OE  MUSCLE.  47 

EXPERIMENT  IX. 

Independent  Irritability  of  Muscle. 

Arrange  the  induction  apparatus  for  tetanizing  current, 
and  connect  a  pair  of  platinum'  electrodes  to  the  secondary 
circuit. 

Experiment. — Kill  a  frog  by  pithing  the  brain  in 
the  presence  of  an  instructor.  (Method  will  be  demon- 
strated.) Have  a  pointed  match  ready,  and  as  soon  as  pith- 
ing needle  is  withdrawn  plug  the  skull  cavity  through  the 

foramen    magnum,    to    prevent 

/^'^X        >  loss  of  blood  and  to  insure  de- 

//        V  X  ,.-■'*  struction  of  the  brain.     If  the 

/(7    Z/^''  V)A'''^  brain   has   been   destroyed,   the 

ly    JCJpU-'l^.-A- ''  frog    will    not    raise    its    nose 

[J       Vp^r      .VJ...  p  from    the    plate,    and    will    not 

y_y      ^VA— ^^^^X^ P  make   spontaneous   movements, 

I'l— -- _g  although    it    will    make    reflex 

Fig.  g.    Relation  of  brain  to        movcments    if    it    be    cxcited. 

skull  of  frog.     A,   cerebral  hemi-  g^t     the     skin     OU     the     back     of 

spheres;    B,    eyes;    C,    thalamen-  i   •     i     i  •        i-       n 

cephaion;  D,  optic  lobes;  E,  left  thigh  longitudmally,  separ- 
benum'':'''G!^^rredX'obTongau^^  atc  the  Semimembranosus  from 
H,  spinal  cord.  l-j^g  ileofibularis  muscle,  and  ex- 

pose the  sciatic  nerve,  (see  Eig.  lo.  Dorsal  View).  Care- 
fully separate  a  portion  of  the  nerve  from  the  surrounding 
tissues  without  injury  to  the  nerve  or  the  blood  vessels. 
Pass  a  ligature  under  the  nerve,  carrying  the  ends  around 
to  the  front  of  the  thigh,  and  tie  tightly,  thus  including  all 
the  structures  of  the  limb  except  the  ner\'e,  (See  Fig.  ii). 
Cover  exposed  nerve  with  filter  paper  moistened  with  salt 
solution. 

Inject  into  the  dorsal  lymph  sac  about  i  cc.  of  a  stock 
solution  of  curara.  Use  for  this  purpose  a  pipette  with 
fine  point  and  rubber  bulb.  To  insert  pipette,  raise  loose 
skin  of  back  over  forward  part  of  dorsal  lymph  sack  with 
forceps,  and  make  small  opening  in  skin  with  scissors.    Lay 


HXPKRIMKNT  TX.  - 


the  frog  on  a  plate  and  cover  it  with  moist  filter  paper.  Ob- 
serve that  pinching  the  toes  of  either  hind  leg  slightly, 
causes  a  contraction  of  the  muscles  of  the  leg  thus  irritated, 
and  that  a  stronger  stimulus  causes  a  contraction  of  the 
muscles  of  both  legs.  Do  not  excite  more  strongly  than  is 
required  to  produce  the  effect. 

As  the  drug  takes  effect,  the  ability  of  the  right  leg  to  re- 
spond to  such  irritation  gradually  becomes  less,  and  after 
20  or  30  mintes  it  ceases  altogether,  although  the  left  leg 
will  respond  as  before.  Notice  especially  whether  a  crossed 
reflex  movement  occurs  in  the  left  leg  after  the  right  leg  is 
paralyzed. 

VENTRAL,  VIEW  DORSAE  VIEW  ; 


Eig.  10.  Dissection  of  right  leg  of  frog.  A,  sciatic  plexus;  B,  cruralis 
sartorius ;  D,  gracilis  magnus ;  E,  gastrocnemius ;  F,  glutaeus  magnus ; 
sciatic  nerve ;   H,   llio-fibularis ;   I,   semimembranosus. 


G, 


When  all  the  body  but  the  left  leg  has  become  com- 
pletelv  paralyzed,  open  the  abdominal  cavity  and  remove 
the  vicera,  care  being  taken  not  to  injure  the  nerves  behind 
them,  (see  Fig.  10.  Ventral  View\  Cut  the  body  in  two, 
leaving  the  last  two  vertebrae  connected  with  the  legs.  Split 
these  vertebrae  lengthwise,  and  holding  the  fragments  with 


INDEPENDENT  IRRITABILITY  OF  MUSCLE. 


49 


forceps,  dissect  out  the  sciatic  plexus  supplying"  the  hind 
legs.  Do  not  take  hold  of  nerves  with  forceps,  and  avoid 
stretching-  them.  Stimulate  the  plexuses  in  turn  with  the 
tetanizing  current.  What  is  the  result?  Now  apply  the 
stimulus  directly  to  the  muscles  of  the  legs.  What  is  the 
result  ? 

Keep  the  preparation,  to  use  in 
Experiment  lo,  which  should  immedi- 
atety  follow  this  one. 

Answer  the  following  questions  in 
your  notes,  and  state  proofs : 

How  did  the  drug  reach  the  leg? 
Does  curara  poison  nerve  fibers? 
Does  it  poison  muscles  ? 
What  does  it  poison? 
Can  curara  paralyze  before  it  pro- 
duces  anaesthesia,   that  is,   when  the 
sensory  nerve  endings,  fibers  and  cen-- 
tral  nervous  mechanisms  are  capable 
of  functioning? 

When  an  electric  current  is  sent 
through  a  non-curarized  muscle,  as  in 
the  preceding  experiments,  what  two 
kinds  of  stimuli  may  act  on  the 
muscle? 


i^/ihj 


Fig.  II.  Diagram  to 
illustrate  effect  of  curara. 
The  shaded  portion  shows 
the  parts  affected  by  the 
drug.  Iv,  ligature  sur- 
rounding the  whole  of 
leg,  except  the  sciatic 
nerve ;  R,  P,  right  sci- 
atic plexus ;  L,  P,  left 
plexus. 


50  IJXPKRIMENT  IX. 


INDEPENDENT  IRRITABILITY  OF  MUSCLE.  5 1 


^2  EXPERIMENT  IX. 


ISOLATED  CONDUCTION  IN   MUSCU:.'  53 

EXPERIMENT  X. 

Isolated  Conduction  in  Muscle. 

Although  the  separate  fibers  of  a  striated  muscle  are  in 
close  contact,  they  are  like  the  nerve  fibres  in  a  nerve  trunk, 
independent  mechanisms.  If  a  fiber  is  excited,  the  condition 
of  activity  which  is  aroused  runs  the  length  of  the  fiber 
in  either  direction  from  the  point  of  excitation,  but  does 
not  spread  to  neighboring  fibers.  This  fact  can  be  demon- 
strated most  readily  on  a  curarized  muscle,  and  by  employ- 
ing unipolar  excitations. 

Apparatus  for  Unipoi,.ar  Excitation. — Arrange  in- 
duction coil  to  give  tetanic  excitations.  Connect  one  pole 
of  the  secondary  coil  by  an  insulated  wire  with  the  binding 
post  on  the  sheet  of  copper.  The  other  pole  of  the  second- 
ary coil  may  be  left  free,  or,  if  a  strong  current  is  needed, 
be  connected  with  a  gas  pipe  and  so  with  the  earth. 

Experiment. — Remove  the  sartorius  muscle  (see  Ven- 
tral View,  Fig.  lo),  from  the  curarized  leg  of  the  frog 
used  in  the  Experiment  IX.  Lay  the  muscle  on  the  copper 
plate.  Start  the  automatic  interrupter  and  lightly  touch  one 
edge  of  the  muscle  for  a  moment  with  the  point  of  a  needle 
or  other  metalic  instrument  with  sharp  point.  The  muscle 
will  be  seen  to  contract  along  the  edge  that  is  touched  and 
to  curl  toward  that  side.  If  the  other  edge  is  touched,  the 
muscle  fibers  will  draw  together  on  the  other  side.  With  a 
reading  glass  one  can  see  that  the  only  fibers  to  contract  are 
those  near  the  point  touched.  By  this  method  of  unipolar 
•excitation  the  current  does  not  flow  in  a  circuit.  The  cur- 
rent enters  the  muscle  wherever  it  is  in  contact  with  the 
copper  plate  (the  indifferent  pole),  but  being  diffuse  fails 
to  excite  it ;  it  leaves  the  muscle,  to  charge  up  the  body  of 
the  experimenter,  at  the  point  that  is  touched  by  the  needle 
(the  active  pole),  and  the  dense  stream  causes  excitation  at 


54  KXPERIMENT  X. 

that  point.  The  strict  hmitatioii  of  the  contraction  process 
to  the  fibers  excited,  shows  that  the  excitation  does  not 
spread  from  fiber  to  fiber. 

Why  is  it  necessary  to  supply  a  curarized  muscle  in  this 
experiment  ? 


ISOLATED  CONDUCTION  IN  MUSCLE.  55 


56  EJXPEJRIMENT  X. 


CONTRACTIONS  OF  NON-STREATED  MUSCLE.  57 

EXPERIMENT  XL 

Contractions  of  Non-Striated  Muscle. 

Apparatus. — Set  up  apparatus  like  that  used  in  Experi- 
ment ITI,  and  in  addition  mount  two  electric  signals  so  as 
to  write  in  the  same  vertical  line  as  the  lever.  Connect  one 
signal  in  the  primary  circuit,  to  mark  the  time  of  stimulation, 
and  the  other  in  the  clock  circuit  to  record  seconds.  Because 
of  the  resistance  of  the  time  signal,  and  the  fact  that  smooth 
muscle  reacts  poorly  to  currents  of  such  brief  duration  as 
induced  currents,  it  will  be  necessary  to  use  two  dry  cells 
in  the  primary  circuit.  No  weight  should  be  used  on  the 
lever. 

Experiments. — Kill  a  frog,  remove  the  stomach,  cut 
off  from  stomach  a  ring  5  mm.  wide,  and  hang  this  ring  of 
non-striated  muscle  on  a  pin  hook  which  has  been  fastened 
vertically  in  the  clamp  intended  for  femur.  Suspend  the 
light  muscle  lever  from  the  ring  by  means  of  a  pin  hook. 
Stick  the  pin  of  the  pin  electrode  through  the  lower  border 
of  the  ring.  Keep  moist  chamber  closed  and  moisten  muscle 
frequently,  as  it  is  so  small  that  it  is  especially  liable  to  be 
injured  by  drying. 

a.  Time  Relations  of  Myogram. — The  drum  is  to  be 
revolved  by  the  clockwork,  and  to^  have  a  rate  of  2  mm.  per 
second.  See  that  writing  points  are  in  the  same  vertical 
line,  and  put  part  of  curve  showing  this  in  your  notes. 
Find  the  latent  period,  and  the  time  oi  the  rise  of  the 
curve.  Remember  that  non-striated  muscle  is  very  readily 
excited  by  mechanical  stimuli  and  that  its  power  to  keep  in 
tonic  contraction  is  much  greater  than  that  of  striated 
muscle.  If  the  ring  is  drawn  together,  wait  for  the  muscle 
to  relax  before  exciting  it.  Watch  tO'  see  if  relaxation  is 
taking  place. 


58  b;xpe;rime:;nt  xi. 

b.  Rate  Required  to  Tetamse. — Set  the  drum  turning 
slowly  and  find  by  experimient  slowest  rate  of  stimulation 
which  will  tetanize  non-striated  muscle.  In  order  to  tetanize, 
a  second  contraction  should  be  called  out  a  short  time  be- 
fore the  preceding  contraction  has  reached  its  full  height. 
If  one  knows  the  latent  period  and  the  contraction  period, 
one  can  make  a  fair  estimate  of  the  required  rate  of  exci- 
tation. 

c.  Spontaneous  Contractions. — Set  the  drum  to  run 
at  the  rate  of  i  mm.  per  second  or  slower,  and  record  a 
series  of  spontaneous  contractions.  Let  the  time  be  recorded 
in  seconds.  Spontaneous  contractions  may  occur  from-  the 
first,  and  interfere  with  the  determination  of  time  relations. 
If  such  is  the  case,  the  only  way  to  secure  the  results  is  to 
give  the  stimuli  at  such  a  time  that  one  can  be  sure  whether 
the  following  contraction  is  a  response  to  the  stimulus  or 
a  spontaneous  contraction. 

How  does  the  latent  period  and  the  contraction  period 
of  this  non-striated  muscle  compare  with  that  of  the  gas- 
trocnemius? What  rates  were  needed  to  tetanize  these 
muscles?  For  comparison  state  in  the  notes  the  values  ob- 
tained in  experiments  VI  and  VII.  What  was  the  rate  of 
the  spontaneous  contractions? 


CONTRACTIONS  OP  NON-STRIATED  MaSCI,E.  59 


6o  E^XPERIMENT  XI. 


WAVK  OF  CONTRACTION   IN  FROC/s  HKj\RT. 


6i 


EXPERIMENT  XIT. 

Frog's  Heart — Its  Structure ;  the  Relative  Time  of  Action 
of  the  Different  Parts. 


Apparatus. — Set  up  as  shown  in  Figure  12,  except  for 
electric  signal  which  wall  be  used  only  in  Experiments  XIV 
and  XV.  Clamp  horizontally  on  short  stand,  the  nickled 
rod  with  hole  for  wire  and  binding  screws  in  end  (A),  letting 
the  free  end  of  the  rod  project  about  7  cm.  beyond  the 
stand.  Place  a  clamp  on  the  end  of  the  rod,  and  fasten 
vertically  in  this  clamp  the  rod  (B)  earning  the  lighter 
muscle  lever.  Thus  arranged  the  lever  can  be  either  raised 
or  lowered,  or  can  be  rotated  so  as  to  bring  the  point  against 
the  drum.    Loosen  the  screw  fastening  the  yoke  (C)  of  the 


Fig.  12.  Apparatus  for  recording  the  beat  of  a  frog's  heart.  A,  horizontal 
rod  carrying  binding  screw  for  wire ;  B,  vertical  rod  carrying  lever ;  C,  yoke 
supporting  axis  of  lever  ;  D,  time  signal ;  IJ,  wire,  connecting  lever  with  button 
to  rest  on  the  heart ;  F,  piece  of  flexible  insulated  wire,  connecting  short  piece 
of  wire,  passing  through  button,  with  binding  post  on  frog  board;  G,  frog 
board. 


62  EXPKRTMENT  .XII. 

lever  to  the  rod,  and  turn  the  yoke  until  it  supports  the 
lever  with  the  tip  2  cm.  below  the  horizontal  plane  passing 
through  its  axis ;  then  turn  the  screw  home.  Now  bring 
the  drum  up  to  the  lever,  and  see  that  v^^hen  it  is  horizontal 
it  has  such  a  height  that  it  can  be  made  to  write  on  any 
part  of  the  drum  by  raising  or  lowering  the  drum.  Clamp 
the  frog  board  (G)  to  the  stand  below  the  lever.  Connect 
the  steel  wire  (B)  of  the  heart  electrode  with  the  lever. 
The  hole  into  which  it  must  be  inserted  will  depend  on  the 
size  of  the  movements  of  the  heart.  The  record  of  the 
movements  should  be  not  less  than  a  centimeter  in  height. 
Fasten  the  piece  of  flexible  insulated  wire  (F)  to  the  bind- 
ing po'St  on  the  frog  board.  Observe  that  the  two  wires 
which  project  through  the  button  may,  when  brought  in 
contact  with  the  heart,  be  used  as  electrodes. 

Opj^ration. — Choose  an  active  frog;  pith  brain  as  de- 
scribed in  Experiment  IX;  cut  off  the  projecting  end  of 
the  match ;  and  put  frog,  back  down,  on  the  plate.  Operate 
at  once,  before  the  effects  of  the  shock  have  passed  off. 
Make  median  skin  incision  from  a  centimeter  above  pubis  to 
one-half  centimeter  below  jaw.  Raise  ensiform  cartilage 
with  forceps,  and  with  sharp  scissors  remove  sternum,  al- 
ways keeping  point  of  scissors  well  away  from  the  pericar- 
dium and  aortae.  In  cutting  through  the  abdominal  wall 
avoid  the  large  vein.  Now  slide  the  heart  lever  up 
out  of  the  way,  and  place  the  frog  on  the  frog  board  so 
that  its  ventricle  lies  directly  beneath  the  button  on  the 
prop  of  the  lever.  With  the  frog  in  this  position,  draw 
the  fore  legs  widely  apart  so  as  to  expose  the  heart  beating 
within  the  pericardium,  and  pin  these  legs  firmly  to  the 
frog  board.  Now  pick  up  the  pericardium  over  the  bulbus 
arteriosus,  and  slit  the  pericardium  throughout  its  length 
with  sharp  pointed  scissors. 

a.     Gross  Anatomy  of  the  Heart. 

Moisten  the  heart  from  time  to  time  with  normal  salt 
solution :  it  must  not  be  allowed  to  dry.  Observe  the  posi- 
tion of  the  bulbus  arteriosus  (//)  and  the  two  aortic  arches 
(A)  ;  the  relation  of  the  two  auricles  (B,  C)  to  each  other 


WAVD  OF  CONTRACTION   IN  FROG's  HF,ART. 


63 


and  to  the  ventricle  (£),  (the  line  of  separation  of  the 
auricles  lies  behind  the  bulbus  arteriosus)  ;  and  the  well 
marked  auriculo-ventricular  groove.  Lift  the  ventricle  with 
a  camel's  hair  brush  moistened  with  saline  solution,  and 
notice  the  place  where  the  vena  cava  inferior  opens  into 
the  sinus  venosus  (F)  ;  the  white  crescentic  line  where  the 
sinus  joins  the  auricle;  also  the  frenum,  a  slender  ligament 
which  attaches  the  dorsal  wall,  of  the  ventricle  to  the  peri- 
cardium. 


Ventral   View 


Fig.  13.  The  gross  anatomy  of  frog's  heart.  (Ventral  view  after  Cyon,  dorsal 
-view  after  Howes.)  A,  aortae ;  B,  right  auricle;  C,  left  auricle;  D,  pulmonary 
vein ;  F, '  ventricle ;  F,  sinus  venosus ;  G,  sino-auricular  valves ;  H,  bulbus 
.arteriosus. 

b.     Origin  and  Course  of  the  Wave  of  Contraction. 

T. — Inspfction. — Try  to  observe  the  place  where  the 
wave  of  contraction  begins,  and  the  order  in  which  it 
spreads  over  the  different  chambers  of  the  heart.  See  that 
when  a  part  contracts  and  drives  the  blood  out,  it  grows 
paler,  while  the  part  receiving  the  blood  swells  and  flushes. 
The  change  of  color  begins  somewhat  later  than  the  process 
causing  it.  Answer  in  your  notes  the  following  questions: 
What  is  the  action  of  the  auricles  during  the  ventricular 
diastole,  and  during  the  ventricular  systole  ?  What  changes 
are  observed  in  the  ventricle  during  auricular  diastole,  and 
during  auricular  systole? 

2. — Thf  Myocakdiogram. — Adjust  the  button  on  the 
prop  of  the  lever  to  the  ventricle,  with  the  prop  vertical  and 
the  lever  horizontal.  Be  careful  that  both  of  the  wire 
points  on  the  under  surface  of  the  button  are  in  contact  with 


64  EXrHRIMENT  XII. 

the  ventricle,  and  that  the  button  does  not  touch  the  auricle 
so  as  to  be  moved  direct!}-  by  it.  Once  rightly  adjusted, 
it  should  not  be  necessary  to  alter  the  position  of  the  lever 
during  the  afternoon.  The  prop  should  be  connected  with 
the  hole  in  the  lever  which  will  give  a  writing  of  one  and  a 
half  to  two  centimeters  in  height.  Record  the  beats  with 
slow,  medium  and  rapid  speeds  of  the  drum,  studying  the 
heart  itself  while  the  curves  are  being  written.  ]\Iark  on  the 
record  the  part  of  the  cardiac  cycle  which  is  responsible  for 
each  wave  of  the  curve.  Xotice  that  the  lever  records  at 
the  same  time  changes  in  the  position,  form  and  volume  of 
the  ventricle.  How  and  why  does  the  beat  of  the  auricle 
show  in  the  curve?  AMiich  part  of  the  curve  was  made  by 
the  ventricular  systole?  Does  the  lever  fall  or  rise  in  the 
ventricular  diastole?     Explain. 


WAVK  OF   COXTRACTIOX   IX  PROG  S   HEART. 


65 


66  liXPERIMUNT  XII. 


Et'FECT  01^  TEMPERATURE  ON  HEART  RATE.  67 

EXPERIMENT  XIII. 
Effect  of  Temperature  on  Heart  Rate. 

a.     Effect  of  Air. 

Pith  a  frog,  and  expose  the  pericardium.  Count  the 
heart  rate.  Role  up  a  tube  of  paper  round  a  pencil,  and  using 
the  tube,  warm  the  heart  by  slowly  breathing  upon  it,  and 
observe  the  change  in  rate.  After  the  new  rate  has  become 
established,  place  the  end  of  the  tube  close  to  the  heart,  but 
without  touching  it,  and  suck  air  over  the  heart.  Note  the 
rate  of  beat. 

h.     Effect  of  Solutions. 

Let  the  heart  take  on  the  temperature  of  the  room, 
and  then  after  counting  the  rate,  place  the  frog  on  his  back 
in  a  shallow  tray,  and  cover  the  heart  Avith  salt  solution 
heated  to  30°  C.  Note  the  rate.  Replace  the  warm  solu- 
tion, by  cold  salt  solution,  10°  C,  and  when  it  has  had 
time  to  cool  the  heart,  again  record  the  rate. 

Put  the  figures  which  you  obtained  in  your  notes,  and 
explain  the  effects  observed.  If  the  heart  is  beating  well 
at  the  close  of  the  experiment,  dry  it  off  and  use  it  in 
the  next  experiment.  The  tray  must  be  cleaned  and  dried 
before  it  is  returned. 


«8 


EXrERi:MEXT    XIII. 


EfFECT  OF  TEMPERATURE  OX   HEART  RATE.  69 


70 


i;xrKRiMKNT  XI I r. 


REFRACTORY   PERIOD.  7 I 

EXPERIMENT  XTV. 
Refractory  Period  and  Compensatory  Pause. 

ApparaTus.^ — ^The  same  apparatus  for  recording  the 
contractions  of  the  heart  may  be  used  as  in  Experiment 
XII.  In  addition  arrange  an  induction  coil  to  give  single 
shocks,  and  connect  a  time  signal  in  the  primary  circuit. 
Adjust  the  signal  to  write  just  below  and  in  the  same  vertical 
line  with  the  heart  lever.  One  cell  in  the  primary  circuit,  with 
the  secondary  coil  pushed  half  way  up,  usually  gives  sufficient 
strength  of  current.  Avoid  using  a  current  stronger  than  is 
required  to  call  out  an  extra  contraction,  otherwise  the  cur- 
rent will  spread  to  the  muscles  of  the  trunk.  One  of  the 
w4res  of  the  secondary  coil  is  to  be  fastened  to  the  binding- 
post  on  the  frog  board,  and  to  be  brought  into  communica- 
tion with  the  ventricle  by  means  of  the  fine  insulated  wire 
passing  to  one  of  the  pins  in  the  button  which  is  to  rest  on 
the  ventricle  (see  Fig.  12)  ;  the  other  wire  is  to  be  fastened 
in  the  horizontal  rod  supporting  the  heart  lever,  through 
which  it  communicates  with  the  heart. 

In  order  that  the  curve  may  be  read  with  accuracy, 
three  things  are  essential,  viz : — the  length  of  the  lever 
must  he  knozmt,  the  relative  position  of  the  writing  points 
must  he  marked  on  the  drum,  and  a  hase  line  must  he 
drawn  with  the  lever  horizontal.  If  the  mark  which  shows 
the  position  of  the  leA^^er  is  a  long  arc,  it  can  be  used  to 
determine  whether  the  base  line  was  properly  drawn,  and 
if  it  was  not,  to  establish  a  correct  base  line.  The  relative 
position  of  the  writing  points  must  be  recorded  on  each 
curve  at  the  beginning  or  end  of  the  experiment.  A  cross 
can  be  written  over  each  of  the  marks  to  identify  them,. 

Experiment. — ^Adjust  lever  to  heart  and  place  drum 
so  that  contractions  will  be  recorded.  Leaving  drum  in 
this  position,  turn  yoke  at  axis  so  that  it  will  support  lever 
horizontally.  Rotate  drum  to  give  base  line,  and  at  beginning 


72  E^XPBRIMKNT   XIV. 

of  curve  mark  a  large  arc  by  raising"  lever,  and  mark  position 
of  time  signal.  Lower  yoke  and  make  experiment.,  Let 
the  drum  run  at  the  rate  of  20  mm.  per  second ;  and  while 
the  heart  records  its  contractions,  stimulate  the  ventricle 
with  single  breaking  shocks  every  fifth  or  sixth  beat,  the 
makes  being  short  circuited,  to  test  the  effect  of  exciting 
it  at  the  following  times — during  the  systole  of  the  ven- 
tricle, and  early  and  late  in  the  diastole  of  the  ventricle. 

State  in  notes  in  which  case  the  stimulus  produces  no 
effect  (the  "Refractory  Period")  ;  and  when  an  extra  con- 
traction. State  relative  size  of  the  contractions  obtained 
in  different  parts  of  diastole.  Notice  that  an  extra  con- 
traction is  followed  by  a  pause,  (the  "Compensatory 
Pause").  Is  the  pause  long  enough  to  compensate  for  the 
extra  contraction,  so  that  the  rhythm  of  the  beat  is  not 
changed  afterward?  Explain  these  phenomena.  Was  the 
auricle  excited  by  spread  of  current? 

The  curve  of  contraction  is  distorted  by  the  fact  that 
the  lever  records  an  arc.  To  determine  the  part  of  a  con- 
traction at  which  a  stimulus  was  applied,  it  is  necessary 
first  to  make  sure  that  the  lever  was  horizontal  when  the 
base  line  was  drawn.  If  the  line  drawn  was  not  correct, 
draw  one  at  the  proper  height.  Draw  a  vertical  line  through 
the  point  of  excitation,  as  given  by  the  time  signal,  to  the 
base  line  which  corresponds  to  the  position  of  the  heart 
lever  when  horizontal,  and  then  having  allowed  for  the 
relative  position  of  the  writing  points,  draw  through  the 
heart  curve  an  arc,  the  axis  of  which  is  on  this  base  line  and 
the  radius  of  which  is  equal  to  the  length  of  the  lever. 


RrifRACTORY    PERIOD. 


73 


74  EXPE^RIMENT   XIV. 


EXCITATION  OF  RESTING  HR.ajRT.  75 


EXPERIMENT  XV. 

iiesponse  o£  the  Resting  Heart  to  Stimulation  by  Induc- 
tion Shocks. 

Apparatus. — Use  apparatus  the  same  as  in  Experiment 
XIV  and  in  addition  mount  a  tuning  foirk  on  large  stand 
above  the  electric  signal.  Prepare  a  frog,  and  expose 
heart,   losing  as  little  blood  as  possible. 

Experiment. — Bring  heart  to  rest  by  tying  a  ligature, 
the  first  Stannius  ligature,  about  the  juncture  of  the  sinus 
with  the  auricles.  To  do  this  pass  ligature  under  the  aortic 
arches  close  to-  the  auricles,  then  pass  the  ends  around  the 
heart  posteriorly,  so  that  the  ligature  lies  at  the  base  of  the 
auricles,  and  tie  a  single  knot  loosely  over  the  crescentic 
line  where  the  sinus  and  the  auricles  join.  Make  sure  that 
the  ligature  is  in  the  proper  place,  then  tighten  and  tie 
securely.  The  heart  should  stop  beating.  If  it  does  not  do 
so  within  a  few  seconds,  tie  a  second  ligature  closer  to  the 
auricles. 

a.     Myogram  of  Heart  Muscle. 

As  soon  as  the  beat  stops,  place  frog  on  board  and  adjust 
the  lever  to  the  heart.  Establish  the  position  of  the  writing 
points  and  draw  a  base  line  as  described  in  Experiment  XIV. 
Move  coil  far  away,  and  find  smallest  stimulus  that  will 
cause  a  contraction,  taking  care  that  the  current  does  not 
excite  the  muscles  of  the  trunk.  Record  the  curve  of  con- 
traction and  beneath  it  the  tuning  fork  curve,  and  the  mo- 
ment of  make  and  break  of  the  primary  circuit,  as  shown 
by  the  signal.  Short  circuit  the  make.  Turn  the  drum  by 
hand  at  rate  of  about  lo  cms.  per  second,  and  excite  by 
the  break.  Assume  that  the  signal  records  the  exact  mo- 
ment of  excitation,  and  calculate  from  the  record  the  time 
relations  of  the  myogram,  as  in  Experiment  VI.  Save  a 
part  of  the  record  which  shows  that  the  writing  points  are 


76  t;xpe;rimij:nt  xv. 

in  the  same  vertical  line,  and  state  in  notes  length  of  lever 
in  millimeters.  In  what  respect  does  the  myogram  obtained 
from  the  heart  differ  from  that  of  striated  muscle? 

b.  Bozv'ditch's  Staircase. 

Stimulate  about  15  times  with  a  medium  strength  of 
current  at  intervals  of  2  to  5  seconds,  recording  on  drum 
moving  2  mm,  per  second.  A  gradually  increasing  height 
of  contraction  is  usually  given,  which  is  called  a  staircase, 
and  explained  as  a  result  of  increased  irritatibility  due  to- 
frecjuent  repetition  of  the  stimulus. 

c.  All  Contractions  Maximal. 

As  soon  as  a  sufficient  number  of  myograms  have  been 
recorded,  remove  the  fork,  and  stimulate  about  ten  times 
with  gradually  increasing  current  at  intervals  of  30  seconds, 
recording  contractions  on  drum  about  i  cm.  apart.  There 
should  be  no  increase  in  height  of  contraction  due  to  in- 
creased stimulus.  Any  stimulus  sufficient  to  cause  heart 
muscle  to  contract,  causes  a  maximal  contraction.  This  is 
often  spoken  of  as  the  law  of  "y\ll  or  none."  See  that  the 
muscles  of  the  trunk  do  not  contract. 

d.  Effect  of  Frequent  Stimidi. 

Connect  wires  of  primary  circuit  with  automatic  inter- 
rupter and  record  the  response  of  the  heart  to  frequent 
stimuli,  using  first  a  weak  and  then  a  medium  current.  See 
that  the  muscles  of  the  trunk  do  not  contract.  Drum 
should  turn  5  mm.  per  second.  Weak  stimuli  should  cause 
separate  beats  and  stronger  stimuli,  increase  of  tonus,  indi- 
cated by  a  higher  base  line. 


KXCITA'J'ION  01'   RESTING   IIKAJJT.  77 


78  Expe;rime;nt  xv. 


MOTOR   POINTS   ON    THE   ARM.  79 

EXPERIMENT  XVI. 
Location  of  a  Few  Motor  Points  on  the  Human  Arm. 

The  few  motor  points  surrounded  by  a  circle  in  the  dia- 
gram (Fig.  17),  are  to  be  located  on  each  arm.  In  doing 
this,  the  unipolar  method  of  excitation  is  to  be  employed. 
To  use  this  effectively,  the  more  efficient  pole  of  the  induc- 
tion coil  will  have  to  be  used. 

The  More;  Ei^j?icient  Pole;  of  an  Induction  Coil. 
When  the  manner  of  winding  and  connecting  wires  with 
posts  can  be  plainly  seen,  the  direction  of  induced  currents 
can  be  found  easily,  for  the  direction  of  the  primary  cur- 
rents can  be  observed  by  inspection  of  the  battery  and  its 
connections,  and  the  induced  current  flows  in  the  opposite 
direction  to  the  battery  current  at  the  time  of  the  make,  and 
in  the  same  direction  at  the  time  of  the  break.  But  in  most 
coils  the  windings  and  connections  are  hidden,  making  it 
necessary  to  determine  the  point  in  question  in  some  other 
way. 

Connect  a  dry  cell  with  a  key  and  a  pair  of  platinum 
electrodes  as  shown  in  Figure   14.     Lay  a  small  piece  of 

^-^^~— „^^  filter  paper  on  a  clean  plate, 

•*  (O'  '~^^__^^^7!^^        "^^       ^^^     slightly     moisten     it 

B  with  only  a  few  drops  of 

Fig.  14.  Apparatus  to  detect  direction       ^  solution  of  Starch  and  pO- 
of  flow   of   current   in    a   simple   circuit.  ... 

A,   dry   cell;    B,   mercury   key;    C,    elec-        tassium    iO'didc.       Draw    the 

ends  of  the  electrodes  slow- 
ly and  lightly  across  the  moistened  paper,  first  with  the 
circuit  open  and  then  with  it  closed.  Observe  the  dark  line 
given  at  the  anode  while  the  current  is  passing,  and  the  ab- 
sence of  color  at  the  cathode.  The  current  decomposes  the 
potassium  iodide,  and  the  iodine,  being  the  acid  ion,  goes 
to  the  anode  and  there  gives  the  color  reaction  with  the 
starch. 

Now  connect  the  cell  to  the  primary  coil  of  induction 
apparatus,  the  anode  with  post  i  and  cathode  with  post  2. 


8o  EXPERIMENT  XVI. 

Connect  the  platinum  electrodes  to  the  posts  of  the  second- 
ary coil.  Place  the  ends  of  the  electrodes  on  the  moistened 
paper  and  make  the  primary  circuit,  then  slide  the  electrodes 
to  a  fresh  place  and  break.  A  dark  dot  will  be  given  at  one 
pole  on  making  and  at  the  other  on  breaking,  but  no  effect 
will  be  seen  during  the  time  the  primary  current  is  flowing. 
Remembering  that  the  color  reaction  indicates  the  anode, 
we  can  determine  the  direction  of  the  current  in  the  second- 
ary circuit  when  the  primary  is  made  and  when  it  is  broken. 
Since  the  excitation  developed  at  the  cathode  where  the 
current  leaves  the  tissue,  is  stronger  than  that  developed  at 
the  anode  where  the  current  enters  it,  and  since  the  break 
induction  shock  is  stronger  than  the  make,  it  follows  that  the 


Fig.  15.  Apparatus  to  detect  direction  of  flow  of  current  in  secondary  coil 
o;  an  induction  apparatvis.  A,  dry  cell;  B,  mercury  key;  C,  primary  coil; 
D,   secondary  coil ;   E,  electrode. 

more  eificicnt  pole  of  the  secondary  circuit  is  the  one  that 
is  the  cathode  ivhen  the  primary  circuit  is  broken.  Make 
a  note  of  this  point,  stating  whether  the  more  efficient  pole 
is  the  one  to  which  the  short  circuit  key  is  attached  or  the 
opposite  one.  Of  course  it  must  be  remembered  that  this 
will  be  true  only  when  the  anode  of  the  cell  is  connected 
with  post  one,  as  in  the  above  test. 

Preparation  of  vSkin. — Since  the  epidermis  when  dry 
offers  great  resistance  to  the  current,  it  is  necessary  to 
moisten  it  thoroughly.  For  this  purpose  use  a  warm  solu- 
tion of  common  salt  and  borax.  The  solution  can  be 
warmed  in  a  granite  dish,  standing  on  a  tripod  over 
a  gas  flame.  Apply  the  solution  with  a  sponge  or  cloth 
to  the  parts  to  be  stimulated  for  at  least  five  minutes ;  or 
a  pad  soaked  in  the  solution  may  be  bound  on.  Unless 
the  skin  is  thoroughly  moistened,  the  stimuli  are  apt  to  be 
painful  and  inefficient.  Do  not  spill  the  solution  on  tables 
or  apparatus. 


MOTOR   POINTS  ON    THE   ARM. 


Apparatus. — Connect  two  dry  cells  and  a  key  to  the 
primary  coil  of  an  induction  apparatus;  and  connect  a  large 
copper  plate  (the  indifferent  electrode),  to  the  less  effi- 
cient pole  of  the  secondary  coil,  and  a  small  brass  electrode 
(the  active  electrode),  to  the  more  efficient  pole. 


Fig.  i6.  Apparatus  for  unipolar  excitation  of  liuman  nerves.  A,  battery;  B, 
mercury  key ;  C,  primary  coil ;  D,  secondary  coil ;  E,  copper  plate  iised  as 
indifferent  electrode  ;  F,  exciting  electrode. 

Experiment. — Locate  the  motor  points  on  the  left  arm 
first.  By  the  motor  point  is  meant  the  spot  at  which  the 
motor  nerve  enters  the  muscle,  or  where  a  nerve  is  most 
accessible  to  the  current.  P'asten  the  copper  plate  by  an 
elastic  band  on  the  back  of  the  left  hand,  putting  a  wet 


Fig.  17.  Diagram  of  location  of  motor  points  on  flexor  side  of  arm.  (After 
Frb.)  A,  median  nerve  in  upper  arm;  B,  flexor  longus  policis ;  C,  median 
nerve  at  wrist ;  D,  ulnar  nerve  in  upper  arm  ;  E,  tilnar  nerve  in  groove  between 
the  internal  condyle  of  the  humerus  and  the  olecranon  process ;  F,  flexor 
profundus  digitorum ;  G,  fl.exor  sublimis  digitorum ;  H,  tilnar  nerve  at  wrist ; 
I,   abductor  minimi  digiti. 

gauze  pad  between  to  prevent  the  metal  from  touching  the 
skin.  Let  your  companion  press  the  active  electrode  firmly 
upon  the  skin  at  the  point  to  be  stimulated,  and  make  and 
break  the  circuit,  first  with  the  secondary  coil  moved  far 
away  and  then  with  it  closer  to  the  primary,  until  a  position 
of  the  coil  is  found  that  gives  a  moderate  breaking  con- 


S2  liXPERIMENT  XVI. 

traction.  As  soon  as  a  suitable  stimulus  is  found,  try  to 
establish  the  motor  points  corresponding  to-  those  marked 
with  a  circle  in  the  diagram.  Find  for  each  point  the 
position  of  the  electrode  at  which  the  best  motor  response 
is  given.  The  stimulating  electrode  must  be  kept  well 
moistened.  If  a  good  contraction  cannot  be  obtained  with- 
out the  sensation  being  painful,  it  indicates  either  that  the 
epidermis  is  not  sufficiently  moistened  or  that  the  right 
position  for  stimulation  has  not  been  found. 

Consult  an  anatomy  and  locate  the  motor  points  on 
the  left  arm  of  each  student.  Mark  the  points  on  the  skin. 
Demonstrate  to  instructor,  and  make  a  diagram  showing 
the  position  of  the  points  which  you  found. 


MOTOR   rOINTS   ON    THK  ARM.  83 


84 


IXXPrCRIMKNT  XVI. 


ELECTRICAL  EXCITATION   OF  HUMAX   MLTSCLrE-. 


85 


EXPERIMENT  XVII. 

Response  of  Human  Muscle  to  Separate  Induction 
Shocks  and  to  a  Tetanizing  Current. 

Wet  the  left  arm  over  the  motor  point  for  the  flexor 
longus  pollicis,  bind  on  a  wet  pad,  and  then  arrange  the  ap- 
paratus. See  that  the  hands  are  dry  in  handling  the  appar- 
atus. 

Apparatus. — I'his  consists  of  an  arm  rest  and  recording 
instruments,  and  the  stimulating  outfit  used  in  Experiment 
XVI.  The  arm  rest  is  to  be  placed  on  the  table  before 
which  the  subject  is  to  stand,  wath  the  recording  apparatus 
to  the  left,  and  the  stimulating  outfit  to  the  right,  with  key 
and  coil  within  easy  reach  of  his   hand.     The  arm   is  to 


Fig.  18.  Arm  rest  for  support  of  hand  and  electrodes.  A,  arm  rest;  B,  hori- 
zontal rod  fixing  hand ;  C,  vertical  rod  on  arm  rest ;  D,  copper  plate,  the  indif- 
ferent pole,  on  which  is  a  gauze  pad;  E,  exciting  electrode;  F,  vertical  rod, 
clamped  to  horizontal  rod  on  the  arm  rest. 

lie  in  supination  on  the  arm  rest,  and  the  hand  is  to  be  fixed 
by  a  horizontal  rod  (B)  which  presses  lightly  on  the  palm, 
and  is  clamped  to  the  vertical  rod  (C)  on  the  arm  rest. 

The  movement  of  the  thumb  is  to  be  transmitted  by  a 
thread,  which  is  fastened  by  a  loop  to  the  thumb  and  passes 
round  a  pulley  (see  Fig.  19)  to  a  muscle  lever,  which  is  con- 
nected by  another  thread  to  a  rubber  band  supported  on  an  L 
rod.  clamped  to  the  same  stand  as  the  lever  and  above  it.  The 
thread  from  the  thumb  is  fastened  to  the  second,  and  that 


86 


EXPERIMENT  XVIT. 


[nj5 


from  the  rubber  band  to  the  third  hole  in  the  lever.  When 
the  flexor  longus  poUicis  contracts,  the  lever  will  be  drawn 
down,  and  when  it  relaxes  the  rubber  band  will  pull  the 
lever  upwards.  A  time  signal  is  to  be  placed  in  the  primary 
circuit  of  the  induction  apparatus  so  as  to  record  makes  and 
breaks,  and  an  indifferent  and  a  stimulating  electode  con- 
nected'with  the  posts  of  the  secondary  coil.  The  copper 
plate  (Fig.  i8,  D),  which  is  to  act 
as  the  indifferent  pole,  is  to  He  on 
■the  arm  rest  in  such  a  position  that 
the  back  of  the  hand  will  press  on 
a  wet  pad  placed  over  the  plate. 
Care  must  be  taken  that  the  pad 
does  not  come  in  contact  with  the 
vertical  rod  on  the  arm  rest  and  that 
the  hand  does  not  touch  the  bare 
copper  of  the  plate.  The  active 
pole  (E)  instead  of  being  held 
in  the  hand,  is  to  be  fastened 
above  the  arm  in  a  clamp  on  a  hor- 
izontal rod,  which  in  turn  is 
clamped  to  a  vertical  rod  (F), 
which  is  supported  by  a  clamp  fast- 
ened to  the  horizontal  rod  at  the 
side  of  the  arm  rest.  This  arrange- 
ment permits  the  exciting  electrode 
to  be  fastened  at  any  desired  point  on  the  arm. 

a.     Making    and   Breaking   Induction   Shocks    of    Various 
Strengths. 

ExPERiivEKN'T. — Put  the  wet  pad  on  the  indifferent  elec- 
trode ;  then  place  the  arm-  on  the  arm  rest,  so  that  the  back 
of  the  hand  rests  on  the  pad ;  and  fix  the  hand  by  fastening 
the  horizontal  rod  across  the  palm.  Adjust  the  active  elec- 
trode over  the  motor  point  of  the  flexor  longus  pollicis  mus- 
cle. Connect  the  thread  to  the  thumb,  and  move  the  arm 
rest  so  that  the  thread  shall  have  the  proper  position  with  re- 
spect to  the  pulley,  and  the  elastic  band  be  slightly  stretched. 
Place  drum  in  position.  The  lever  should  point  slightly  up- 


Fig.  19.  Apparatus  for  re- 
cording movement  of  thumb. 
G,  rubber  band  supported  by 
L,  rod ;  H,  recording  lever ; 
I,  time  signal ;  J,  puUy ;  K, 
thread   to   thumb. 


KI,1^CTRICAI,  EXCITATION   OF  HUMAN    MUSCI^.  87 

ward,  so  that  when  drawn  down  it  will  keep  in  contact  with 
the  drum.  The  subject  handles  the  key  and  coil  while  his 
associate  has  charge  of  the  kymograph,  and  turns  the 
drum  by  hand.  To  stimulate,  close  to  the  key,  wait  2  or  3 
seconds,  then  open  and  wait  10  seconds.  The  student  attend- 
ing to  the  kymograph  should  keep  track  of  the  time  with 
his  watch  and  tell  the  subject  when  to  stimulate.  Begin 
with  the  coil  placed  so  as  to  give  no  effect,  and  move  it  up 
a  short  distance  after  each  time  the  circuit  is  broken.  The 
signal  marks  the  time  of  stimulation,  and  thus  shows  what 
stimuli  fail  to  give  contractions.  In  case  insufficient  current 
is  obtained,  cut  out  the  time  signal.  Unless  the  current 
causes  too  much  discomfort,  continue  until  both  making 
and  breaking  contractions  of  fair  size  are  recorded.  During 
the  experiment  the  arm  should  be  completely  relaxed.  Volun- 
tary movements  should  be  avoided  as  far  as  possible,  and 
should  be  noted  when  they  occur. 

b.     Tetanising  Current. 

Apparatus. — Connect  battery,  key,  and  signal  with  the 
automatic  interrupter  of  the  induction  coil. 

ExPERiMKNT. — Moisten  electrodes.  Choose  strength  of 
current  sufficient  to  cause  a  tetanic  contraction.  Start  drum 
at  fast  speed  and  obtain  a  record. 


88  ■  EJXPERIMENT  XVII. 


Er^ECTRICAI,  EXCITATION  OF  HUMAN   MUSCI,!;. 


90 


KXPKRIMKNT   XVII. 


^ 


GAI^VANI  S  EIXPBRIMENT.  9 1 

EXPERIMENT  XVIII. 
Galvani's  Experiment. 

Arrange  apparatus  as  shown  in  the  diagram,  making 
sure  that  the  zinc  rod  and  brass  hook  are  bright  and  clean. 

Kill  a  frog,  open  the  abdomen,  and 
remove  the  viscera  from  the  posterioir 
part,    taking   care   not   tO'   injure   the 
^         ^   ^  nerves.     Cut  the  body  in  two  trans- 

versely, ^  cm.  above  the  point  of  exit 
of  the  nerves  from  the  spinal  column. 
Remove  the  skin  from  the  lower  part 
of  the  body,  cut  a  small  slit  through 
the  back  between  the  nerve  plexuses 
and  the  urostyle,  and  hang  the  prepar- 
ation by  this  slit  upon  the  brass  hook. 
Adjust  the  zinc  rod  so  that  upon  giv- 
Fig.  20.  Apparatus  iug  the  preparation  a  slight  swing  the 
n°:nt.^l'1rassTook:  outside  of  the  thigh  near  the  knee  will 
zrni'rod'^  °"  ^  ™'^'  ^'  Strike  it.  Set  the  preparation  swing- 
ing. Upon  each  touch  of  the  leg 
against  the  zinc  rod  a  contraction  should  occur,  throwing 
the  preparation  away,  and  this  should  be  repeated  every 
time  the  swing  brings  the  leg  against  the  zinc. 

We  have  here  two  unlike  metals  moistened  by  a  liquid 
which  is  practically  continuous  through  the  tissues  of  the 
preparation ;  in  other  words,  we  have  the  essentials  of  what 
is  called  a  Galvanic  battery.  This  experiment  is  of  consid- 
erable historical  interest,  for  it  was  the  observation  of  the 
contraction  of  frogs'  muscles  in  a  similar  case,  that  led 
Galvani  to  make  his  famous  studies  of  what  he  supposed 
to  be  animal  electricity,  and  which  was  followed  later  by 
the  invention  of  the  first  battery  by  Volta. 

We  see  here  that  a  battery  current,  like  an  induced  cur- 


oD 


92  EXPERIMENT  XVIII. 

rent,  is  able  to  excite.     In  the  next  few  experiments  the 
effects  of  the  direct  battery  current  upon  nerve  and  muscle 
will  be  observed.    Save  the  preparation  for  the  next  experi- 
ment if  made  the  same  day. 
No  notes  required. 


GALVANl's   DiXPERIMJJNT.  93 


94  EXPERIMENT  XVIII. 


POLARIZATION   01^  ELECTRODES.  95 


EXPERIMENT  XIX. 

Polarization  of  Electrodes. 

a.     Polai'kable  Electrodes. 

Apparatus. — Fasten  two  short  wires  tO'  the  posts  inside 
a  rnoist  chamber  and  place  the  free,  bare  ends  so  that  a 
nerve  can  be  laid  across  them,  i.  e.,  arrange  these  wires  to 
be  used  as  polarizable  electrodes.  Connect  the  binding  posts 
on  the  bottom  of  the  moist  chamber  with  two  dry  cells  and 
a  key.  Make  the  connections  so  that  the  current  shall  flow 
from  the  carbon  (-f-  pole)  to  the  electrode  which  will  be 
nearer  the  muscle.  This  will  then  be  the  anode,  and  the 
current  an  ascending  current,  one  which  will  pass  up  the 
nerve,  and  leave  it  by  the  negative  pole,  the  cathode,  and  so 
flow  back  to  the  battery. 

Experiment. — Make  a  nerve-muscle  preparation  from 
the  frog  used  in  the  preceding  experiment.  The  method  oi 
making  preparation  will  be  demonstrated.  Never  take  hold 
of  the  nerve  with  the  forceps,  and  avoid  stretching  it.  Place 
the  preparation  in  the  moist  chamber,  and  let  the  nerve  rest 
across  the  two  copper  wires.  Avoid  stretching  the  nerve 
and  protect  it  from  drying,  or  its  irritability  will  be  altered. 
P)ring  the  writing  point  of  the  lever  against  a  drum,  and 
arrange  the  kymograph  to  turn  the  drum  2  mm.  per  second. 
Start  the  kymograph,  and  let  it  run  continuously  until  the 
end  of  the  experiment.  Close  the  key  and  let  the  current 
flow  throngh  the  nerve  for  sixty  seconds.  Mark  on  the 
dnmi  the  point  at  which  the  key  is  closed,  C,  and  the  point 
at  which  it  is  opened,  0,  whether  a  contraction  occurs  or  not. 


96  EXPERIMENT  XIX. 

Then  disconnect  the  wires  from  the  battery,  and  connect 
both  of  the  wires  from  the  binding  posts  on  the  moist 
chamber  with  the  key.  Immediately  begin  closing  and 
opening  the  key  regularly,  once  a  second.  If  contractions 
result,  continue  until  they  cease.  Notice  whether  the  con- 
tractions arc  given  on  closing  or  on  opening  the  key,  or 
both,  and  mark  them  accordingly,  C  and  0,  since  it  is  now 
the  polarization  current  which  is  closed  and  opened. 

Notice  carefully,  throughout  the  experiment  any  change 
in  the  character  of  the  contraction  following  closing  and 
opening  the  circuit.  The  contractions  observed  after  the 
battery  has  been  disconnected  are  caused  by  a  current  going 
in  the  opposite  direction  from  the  battery  current,  i.  e.,  a 
descending  current.  This  current  results  from  electrolysis 
which  has  taken  place  at  the  points  of  contact  of  the  nerve 
with  the  wires.  The  condition  set  up  at  these  points  by  the 
passage  of  the  battery  current  is  analagous  to  that  taking 
place  in  a  storage  battery,  when  it  is  charged,  and  the  wires 
are  said  to  be  polarized.  In  order  to  avoid  such  disturbing 
currents  it  is  necessar)'.  whenever  the  direct  current  is  used 
as  a  stimulus,  to  employ  non-polarizable  electrodes. 

b.     A'on-I'olaricable  Electrodes. 

Apparatus. — The  non-polarizable  electrodes  used  in 
this  course,  consist  of  two  boot-like  pieces  of  porous  baked 
clay,  hollowed  at  the  top  to  hold  a  solution  of  zinc  sulphate, 
in  which  two  small  pieces  of  zinc  are  immersed.  The  boots 
of  the  non-polarizable  electrodes  should  have  stood  for  some 
time  in  physiological  salt  solution,  so  that  they  are  thorough- 
ly saturated  with  it  at  the  time  they  are  employed.  When 
they  are  to  be  used,  dry  the  glazed  tops  thoroughly ;  put  the 
metal  clips  on  the  tops  of  the  boots ;  fasten  the  clips  on  a 
glass  rod ;  and  fix  the  rod  in  a  clamp  on  the  support  which 
holds  the  muscle  clamp,  in  the  moist  chamber.  (See  Fig.  21.) 


rOLARIZATlON   OF  EI,KCTRODTiS. 


97 


Dry  the  wires  just  used  as  electrodes,  and  connect  them 
to  the  zincs ;  with  a  dropper  put 
about  half  a  cubic  centimeter  of 
zinc  sulphate  into  the  boots,  being 
careful  not  to  spill  any  of  it  on  the 
outside  of  the  electrodes.  Then  in- 
sert the  zincs  into  the  tops  of  the 
boots. 

Experiment. — Lay  the  nerve 
across  the  tips  of  the  boots  and  re- 
peat the  experiment  made  before. 
If  the  electrodes  are  non-polariz- 
able,  closing-  and  opening  the  bat- 
ter}- circuit  should  give  the  same 
effect  as  before,  but  there  should 
be  no  response  to  the  movements 
of  the  key  after  the  battery  has 
been  removed  from  the  circuit. 
On  completing  the  day's  work, 

the  non-polarizable  electrodes  must  be  thoroughly  washed 

and  returned  to  the  normal  salt  solution. 


Fig.  21.  Method  of  arrang- 
ing non-polarizable  boot  elec- 
trodes in  moist  chamber.  A, 
zinc;  B,  porcelain  boot;  C, 
nerve ;  D,  wires  to  key. 


Pfluger's  Law. 

The  polarization  current  which  is  set  up,  is  strongest  at 
first  and  gradually  fades  away ;  consec[uently  in  the  course 
of  an  experiment,  the  student  often  sees  the  effects  of  the 
opening  and  closing  of  strong,  medium,  and  weak  currents. 
These  effects,  which  differ  with  the  direction  in  which  the 
current  flows  through  the  nerve,  have  been  classed  under 
what  is  known  as  Pfliiger's  law.  To  recall  this  law  one 
has  only  to  remember  the  following  facts : 

I.  The  closing  excitation  develops  in  the  nerve  in  the 
region  of  the  cathode,  and  the  opening  excitation  near  the 


9°  £;XPERIMKNT    XIX. 

anode,  the  irritability  rising-  at  the  cathode  when  the  current 
is  closed,  and  at  the  anode  when  the  current  is  opened  (See 
Fig.  22). 

2.  The  closing-  excitation  is  the  stronger,  the  rise  of 
irritability  at  the  cathode  when  the  current  is  closed,  being 
greater  than  the  rise  at  the  anode  when  the  current  is  opened. 


K 

/p Q) — .V-^ 


TT 
Open 


Close 
Wea/c  X. 


X      JyTedium 


SJron 


^ 


Open      A 


Fig.  22.  Pfliiger's  lyaw.  The  two  upper  diagrams  show  the  effect 
of  ascending,  and  descending,  weak,  medium,  and  strong  direct  battery 
currents  on  the  excitability  and  conductivity  of  a  nerve.  A,  positive 
pole,  the  anode ;  C,  negative  pole,  the  cathode ;  K,  key ;  X,  stimulus 
eft'ective ;  O,  stimulus  ineffective.  The  two  lower  diagrams  indicate 
the  irritability  at  the  anode  and  cathode,  when  the  key  is  closed  and 
the  current  is  flowing  through  the  nerve,  and  the  after  effect  following 
the  opening  of  the  key. 


3.  By  strong  currents  the  conductivity  like  the  irrita- 
bility of  the  nen.^e  is  lessened  at  the  anode  during  the  flow 
of  the  current,  and  at  the  cathode  at  the  instant  that  the 
current  ceases. 

4.  With  an  ascending  current  the  anode  is  nearer  the 
muscle,  and  with  a  descending  current  the  cathode  is  nearer 
the  muscle. 


POLARIZATION   OF  I;r,KCTROD!'.S.  99 


lOO  KXPF.RIMENT  XIX. 


RESrONSE  OE  NERVE  TO  DIRECT  CURRENT. 


lOI 


EXPERIMENT  XX. 

Response  of  Nerve  Upon  Closing  and  Opening  the  Direct 
Battery  Circuit  with  Currents  of  Various  Strengths. 

Apparatus. — ^Use  the  ordinary  apparatus  for  recording 
muscle  contractions.  Introduce  a  rheocord  into  the  circuit 
of  a  battery  of  two  cells,  making  connections  as  indicated 
in  Fig.  23.  Mount  a  pair  of  non-polarizable  electrodes,  in 
the  moist  chamber,  connecting  the  wires  so  that  the  current 


—       E 


Fig.  23.  Method  of  using  rheocord.  A,  German  silver 
wire;  B,  sHder ;  C,  double  binding  post  at  lower  end  of 
German  silver  wire;  D,  battery;  E,  key;  F,  nerve  bridg- 
ing the  boot  electrodes,  the  current  being  ascending. 


will  ascend  the  nerve.  Observe  that  the  current  passes 
down  the  fine  German  silver  wire  of  the  rheocord  to  the 
slider  (B)  and  there  divides,  part  going  to  the  nerve  and 
part  going  through  the  lower  part  of  wire.     At  the  double 


I02  EXPERIMENT  XX. 

post  (C)  at  bottom  of  the  wire,  the  two  streams  of  the  cur- 
rent unite  again  and  pass  together  to  the  battery.  Observe 
that  the  current  traversing  the  nerve  must  increase  as  the 
sHder  is  moved  upward,  because  the  resistance  in  the  wire 
below  the  point  (B)  where  the  circuit  divides  is  increased. 
Experiment. — Since  the  direct  current  rapidly  changes 
the  irritability  of  a  nerve,  the  following  Cautions  must  be 
observed : 

I. — Do  not  apply  the  current  at  all  except  when  you 
wish  a  record. 

2. — Do  not  let  the  current  flow  longer  than  is  absolutely 
necessary. 

3. — Obtain  the  record  by  comparatively  few  stimulations. 

4. — Do  not  excite  oftener  than  once  in  15  seconds. 

Move  the  slider  to  the  bottom,  then  close  and  open  thfe 
key.  There  should  be  no  response.  Move  slider  up  2  or 
'3  cm.  and  repeat.  Continue  in  this  manner,  and  mark  on 
the  curve  the  positions  of  the  slider  at  which  minimal  and 
maximal,  closing  and  opening  contractions  were  obtained. 
Record  as  in  Experiment  III.  Did  the  closing  or  opening 
contraction  appear  first  .^  Did  Wundt's  closing  or  Ritter's 
opening  tetanus  show?  If  your  preparation  reacts  well, 
and  if  you  like,  you  mav  observe  the  facts  tabulated  as 
Pfliiger's  law  (see  Exper.  XIX)  ;  this  is  not  required,  how- 
ever. 


RKSPONSr,  01'    NF.RVK  TO  DIRF.CT   CURRliNT.  IO3 


I04  EXPERIMENT  XX. 


RESPONSE  OF  HUMAN  NKRVKS  TO  DIRRCT  CURRENT.      105 


EXPERIMENT  XXI. 

Stimulation  of  Human  Nerves  by  a  Direct  Current. 

Apparatus. — The  electric  current,  which  is  to  be  used, 
is  supplied  from  a  dynamo  giving  60  volts. 

Key  G,  Fig.  24,  controls  the  flow  of  the  current  to  the 
rheostat.  In  the  rheostat  it  is  shunted,  the  current  passing 
through  the  resistance  from  P  to  N,  and  a  portion  of  it  being 
led  off  through  the  metal  slider  H  to  the  post  PP,  which 
gives  the  branch  of  current  to^  the  arm  circuit.  The  resistance 
in  the  rheostat  is  equivalent  to  the  German  silver  wire  of 
the  rheocord  used  in  Experiment  XX. 

Note  that  as  the  slider  is  moved  clockwise^  the  resist- 
ance between  the  slider  and  post  A^  increases  and  hence 
more  current  mill  so  to  the  arm. 


Fig.  24.  Apparatus  for  stimulation  of  human  nerves  by  a  direct  current. 
G,  key;  P,  post  where  current  enters,  and  N,  where  it  leaves  rheostat;  PP, 
post  connected  with  slider,  from  which  current  goes  to  milammeter ;  H,  slider ; 
I,  milammeter ;  J,  commutator  for  reversing  current ;  K,  L,,  electrodes ;  NN, 
pole  on  rheostat  connected  with  N  and  receiving  current  returning  from 
commutator. 


In  flowing  to  the  arm,  the  current  passes  through  the 
milammeter  I,  and  then  to  the  commutator  J,  through 
which  it  is  carried  to  one  or  the  other  of  the  arm  electrodes, 
according  to  the  direction  in  which  the  bridge  is  rocked.  If 
the  bridge  is  rocked  towards  the  electrodes,  K  becomes  the 
positive  electrode,  the  anode,  and  L  the  cathode ;  if  it  be 
rocked  away  from  the  electrodes,  the  current  goes  through 
the  crossed  wires,  and  I^  becomes  the  anode  and  K  the 
cathode.    In  both  cases  the  current  returns  from  the  cathode 


Io6  EXPERIMENT  XXI. 

In'  way  of  the  commutator  to  the  pole  NN  of  the  rheostat, 
and  thence  to  the  pole  N  and  so  away. 

Experiment. — When  ready  for  this  experiment  report 
to  instructor.  Two  stimulating  electrodes  are  used,  one 
being  applied  to  each  arm,  over  either  the  median  or  the 
ulnar  nerve  near  the  wrist.  Choosing  the  nerve  which  in 
the  preceding  experiment  gave  the  best  results,  and  using 
your  own  induction  coil,  ascertain  again  the  exact  points 
on  the  two  arms  giving  the  best  motor  response.  Mark 
these.  Wet  the  places  on  the  two^  arms  again  thoroughly 
by  binding  a  wet  pad,  moistened  with  warm  salt  solution, 
on  each,  and  while  the  skin  is  becoming  saturated,  study  the 
apparatus.  See  that  hands  are  dry  zvhen  apparatus  is 
handled.  Bring  slider  against  flat  side  of  checking  post, 
and  see  that  the  key  is  open.  Then  place  the  arms  on  the 
arm  supports  (see  Fig.  i8)  and  pressing  the  electrodes 
firmly  over  the  motor  points,  make  the  electrodes  fast. 

In  making  the  experiment  the  subject  sits  quietly, 
watches  for  the  first  appearance  of  sensation  or  contraction 
resulting  from  the  stimuli,  and  reports  at  which  pole  it 
occurs.  The  other  student,  who  is  the  experimenter,  handles 
the  key  and  rheostat,  reads  the  milammeter,  and  records  the 
results  in  a  table  of  the  following  form,  stating  the  number 
of  milliamperes  required  to  produce  the  effect  sought.  The 
red  scale  of  the  milammeter  is  the  one  to  be  observed. 

table  oe  strengths  oe  current  required  to  produce 

eeeect. 

Physical  Anode  on hand 

SENSATION.  CONTRACTION. 

Cathode  closing  , 
Anode  closing  .  , 
Anode  opening  , 
Cathode  opening 

When  all  is  ready  the  experimenter  closes  and  opens 
key.  There  should  be  no  movement  of  milammeter  needle 
and  no  eft'ect  at  electrodes.  He  then  advances  the  slider 
a  short  distance,  closes  the  key,  saying  "close,"  then  as 
soon  as  the  milammeter  reading  can  be  made,  opens  the 


RESPONSE  OF  HUMAN  NERVES  TO  DIRECT  CURRENT.      107 

key  and  says  "open."  Experimenter  must  watch  milam- 
meter,  leaving  subject  to  report  effects.  If  the  current  is 
allowed  to  flow  too  long",  there  are  changes  in  irritability 
which  destroy  the  value  of  the  results.  Advance  slider 
again  and  stimulate  again.  Continue  in  this  way,  trying 
to  find  the  least  current  that  will  give  the  effects  mentioned 
in  the  table.  Of  course  the  experiment  must  stop  when  the 
stimulus  causes  too  much  discomfort  COC  (cathode  opening 
<:ontraction),  is  usually  not  obtained  for  this  reason.  No 
graphic  record  is  taken.  When  table  is  completed,  return 
slider  to  place  of  starting,  rock  the  commutator,  to  reverse 
the  current,  then  stimulate  with  various  strengths  of  current 


Current  dense 
CCC   I 


Current  diffuse 

COC  rar 


Fig.  25.  Diagram  of  paths  taken  by  direct  current  applied  to  human  skin 
over  nerve,  and  of  place  where  current  takes  effect.  _|_,  positive  electrode,  the 
physical  anode,  on  left  arm ;  . — ,  negative  electrode,  the  physical  cathode,  on 
right  arm;  a,  a,  a,  physiological  anodes;  c,  c,  c,  physiological  cathodes;  I, 
CCC,  closing  excitation  where  current  is  dense ;  II,  ACC,  closing  excitation 
where  current  is  diffuse ;  III,  AOC,  opening  excitation  where  current  is 
dense;   IV,   COC,   opening  excitation   where  current   is   diffuse. 


as  before.  Observe  that  the  order  of  appearance  of  CCC, 
ACC,  AOC,  COC,  are  the  same  as  before,  but  that  they 
appear  at  the  opposite  hand.  Do  not  take  time  to  read 
milammeter  in  the  second  test.  Table  is  to  be  made  out 
for  each  student,  and  each  reports  results  obtained  by  the 
experiment  on  himself. 

To  understand  the  results  it  is  necessary  to  recall  the 
following  facts,  as  illustrated  in  Fig.  25 : 

The  first  letter  of  the  ACC  and  AOC,  refers  to  the 
positive  electrode,  the  physical  anode  (see  large  A),  and  the 
first  letter  of  CCC  and  COC,  refers  to  the  negative  electrode, 
the  physical  cathode,  (see  large  C). 

The  second  letter,  C  or  O,  refers  to  the  closing  or  the 
opening  of  the  circuit.     On  closing  the  circuit,  the  stimulus 


io8  }i;xPERiM£;N'r  xxi. 

is  developed  at  the  point  that  the  current  leaves  the  nerve, 
that  is  at  the  physiological  cathode,  (see  small  c,  c.  c)  and 
on  opening  the  circuit,  the  stimulus  develops  where  the  cur- 
rent enters  the  nerve,  at  the  physiological  anode  (see  small 

In  experiment  XX,  you  saw  that  the  closing  contractions 
came  with  weaker  currents  than  the  opening,  and  the  same 
should  be  seen  in  this  experiment,  CCC  and  ACC  should  be 
obtained  with  weaker  currents  than  COC  and  AOC.  There 
are  two  places  where  closing  stimuli  might  develop,  at  the 
physiological  cathodes  (c,  c,  c),  under  the  physical  anode 
(A)  and  at  the  physiological  cathodes  (c,  c,  c),  under  the 
physical  cathode  (C).  Since  the  current  would  be  denser 
where  it  left  the  nerve  under  C  than  where  it  left  it  under  A, 
CCC  should  come  with  a  weaker  current  than  ACC.  For 
a  similar  reason  AOC  should  come  with  a  weaker  current 
than  COC. 


K1':SP0NSe;  01?  human  N^RVIiS  TO  DIRECT  CURRENT.      I09 


no  EXPERIMEJNT  XXI. 


CURRlvNTS  Olf  RF^ST  AND  ACTION.  Ill 

EXPERIMENT  XXIT. 
Currents  of  Rest  and  Currents  of  Action, 

a.     Current  of  Rest  detected  by  Rheoscopic  Frog  Prepar- 
ation. 

Apparatus. — Mount  on  short  stand  a  brass  L  rod,  and 
fasten  a  muscle  damp,  with  the  jaws  horizontal,  to  the 
short  arm  of  the  rod.  Connect  a  dry  cell  and  a  key  with 
an  induction  apparatus  so  as  to  give  tetanizing  excitations, 
and  connect  a  pair  of  electrodes  with  the  secondary  coil. 

Experiment. — Prepare  (A)  a  nerve-muscle  preparation, 
( B)  a  nerve-leg  preparation  (a  "rheoscopic  frog"  prepar- 
ation, which  consists  of  a  leg  intact  from  knee  down,  and 
the  sciatic  nerve),  and  (C)  a  piece  of  thigh  muscle  having 
one  uninjured  surface  and  one  surface  cut  squarely  across 
the  fibres.  To  prevent  drying,  put  between  layers  of  filter 
paper  moistened  with  physiological  salt  solution.  Place  knee 
joint  of  B  in  clamp  with  leg  pointing  upward  and  nerve 
hanging  below.  Avoid  clamping  the  nerve.  Place  C  on 
a  glass  slide ;  make  a  fresh  cross  section  on  C;  then  hold- 
ing glass  slide  in  hand,  bring  C  up  beneath  B  in  such  a 
way  that  the  nerve  of  B  shall  fall  suddenly  across  cut  sur- 
face and  normal  surface  of  C.  B  should  contract,  because 
the  injured  part  of  the  muscle  C  is  undergoing  katabolic 
change  and  is  consequently  negative  as  compared  with  the 
normal  surface.  The  nerve  closes  the  circuit  and  is  stimu- 
lated by  the  so-called  "Current  of  rest,"  the  "Demarcation 
current." 

b.     Current  of  Action  detected  by  Rheoscopic  Frog  Prepar- 
ation. 

Mount  the  glass  side  in  holder  on  L  rod,  and  the  rod 
on  a  stand.  Place  A  upon  the  slide,  and  clamp  the  L  rod 
so  that  the  nerve  of  B  lies  lengthwise  upon  the  muscle  of  A. 


112  e;xpf,rimt;nt  xxit. 

Stimulate  nerve  oi  A  with  tetanizing  current  of  medium, 
strength.    Both  muscles  should  be  tetanized. 

To  find  if  currents  spreading  from  electrodes  have 
caused  B  to  contract,  ligature  nerve  of  A  tightly  at  its 
middle,  with  a  moist  ligature,  and  then  stimulate  above 
ligature.  No  contraction  of  A  or  B  occurs.  A  moist  ligature 
would  not  block  an  electric  current,  but  by  breaking  the 
continuity  of  the  nerve  fibers,  it  effectually  blocks  a  nerve 
impulse.  It  follows  that  B  must  have  been  stimulated  by 
the  "Current  of  action"  the  "Negative  variation  Current,"' 
of  the  muscle  A.  When  A  contracts,  a  wave  of  con- 
traction passes  over  it,  and  at  a  given  instant,  some  parts 
are  undergoing  greater  cataboHc  change  than  others,  and 
hence  are  electrically  negative  as  compared  with  the  less 
active  parts.  The  nerve  completes  the  circuit  and  is  stimu- 
lated. 


cuKRn;N'rs  or*  rf.st  and  action.  113 


114 


EXPKRIMKNT  XX [1. 


re;i^i,ex  frog.  115 

EXPEIMMENT  XXIII. 
The  Reflex  Frog. 

The  value  of  this  experiment  is  great  if  it  be  properly 
interpreted.  Through  it  we  have  the  best  physiological 
evidence  of  the  method  of  spread  of  reflex  processes  in  the 
spinal  cord.  When  studying  the  movements  which  result 
from  excitation,  one  should  try  to  recall  the  finer  anatomy 
of  the  spinal  cord,  the  longitudinal  paths  of  conduction,  the 
method  of  communication  betv/een  the  posterior  and  anterior 
roots,  and  the  way  impulses  pass  from  side  to  side  of  the 
cord. 

a.  Time  of  Recovery  from  Shock. 

Pith  a  frog's  brain  and  plug  cavity  of  skull  with  as  little 
loss  of  blood  as  possible,  (see  Exper.  IX).  Note  the  time 
at  which  this  is  done.  Place  the  frog  on  a  plate,  back  up- 
wards, and  with  the  legs  stretched  out  at  full  length.  Note 
the  time  required  for  recovery  from'  the  shock,  as  shown  by 
the  drawing  up  of  the  legs.  Now  cover  with  moist  paper 
and  leave  for  half  an  hour.  At  the  end  of  this  time  observe 
the  frog's  position.  If  cerebrum  and  cerebellum  have  been 
completely  destroyed,  it  will  lie  zvith  nose  against  plate;  if 
turned  on  back  it  will  not  turn  over;  if  thrown  in  water  it 
will  not  try  to  swim ;  if  stimulated  it  Vv^ill  move  legs  but  not 
jump;  the  power  to  perform  the  most  highly  coordinated 
movements  is  absent. 

b.  Spread  of  Reflexes. 

Clamp  nickled  L  rod  on  stand,  and  put  frog-hook  on 
short  arm  of  L.  Suspend  the  frog  from  hook  passed 
through  nose.  Gently  irritate  flank  with  a  needle  and  ob- 
serve local  twitching  of  muscles ;  excite  more  strongly  and 
notice  spread  of  reflexes  to  limbs.  Pinch  a  toe  gently  and 
then  more  strongly  (do  not  crush)  and  observe  and  note  the 
order  in  which  the  dift'erent  parts  of  the  leg  and  of  the  body 
respond  to  the  excitation. 


ii6  expe;rim£;nt  xxiii. 

c.  Are  Reflexes  Piirposefiil? 

Place  beneath  frog  a  battery  jar  two  thirds  full  of  water, 
so  that  by  lifting  the  jar  the  body  can  be  washed.  Caution. 
— In  this  and  the  following  tests  requiring  the  use  of  acid, 
be  sure  to  wash  it  off  after  each  test.  Put  a  bit  of  paper  two 
mm.  square,  wet  in  io%  acetic  acid  on  right  flank,  left  flank, 
median  line  of  lower  back,  and  on  various  parts  of  leg,  and 
state  in  your  notes  the  results.  Hold  right  foot  lightly  and 
put  paper  on  the  right  flank.  Reflex  should  appear  in  right 
leg,  and  later  in  the  left  leg.  The  word  purposeful  in  the 
question  heading  this  section  is  not  used  in  the  sense  of 
well  adapted  to  the  needs  of  the  animal,  but  directed  by 
volition  to  accomplish  a  definite  object.  In  short,  do  the 
movements  of  the  frog  justify  the  view  that  the  spinal  cord 
is  the  seat  of  intelligence? 

d.  Reflex  Time. 

Immerse  tip  of  longest  toe  in  o.i%  H^SO^  up  to  a 
definite  mark,  noting  number  of  seconds  between  immersion 
and  withdrawal.  Repeat  five  times  with  each  foot  and  re- 
port average  for  each.  Immerse  to  the  same  mark  each 
time,  as  the  distance  affected  influences  the  result.  Wash 
off  the  acid  after  each  test.  Where  is  the  time  probably  lost? 
Does  the  experiment  favor  the  "neuron  theory,"  or  the 
theory  of  a  continuous  nervous  network? 

e.  Spasm  of  Muscles  versus  Cooodinated  Movements. 
Apparatus. — Arrange  induction  coil  to  give  tetanizing 

excitations.    Connect  a  pair  of  electrodes  with  the  secondary 
coil. 

Expi;RiMENT. — Remove  frog  from  hook.  Open  abdo- 
men by  cutting  away  whole  of  anterior  wall ;  remove  vicera 
without  injuring  the  sciatic  plexuses  behind  them.  Cut 
through  the  middle  of  the  sciatic  plexus  on  one  side,  and 
free  the  nerves  so  that  they  can  be  laid  across  a  pair  of 
electrodes.  Put  frog  on  hook.  Apply  electrodes  first  to  the 
peripheral,  and  after,  to  the  central  cut  ends  of  the  nerves 
of  the  plexus,  taking  care  to  use  the  zveakest  effective  tetan- 
ising  current  and  to  avoid  touching  the  electrodes  to  any- 
thing except  the  nerves.  Explain  how  the  resulting  move- 
ments differ. 


REfr.EX  FROG.  iry 


Il8  I'XPI\R1MENT  XXIir. 


REACTION    TIM]i   TO   SOUND. 


119 


EXPERIMENT  XXIV. 


Reaction  Time  to  Sound. 


Apparatus. — Blacken  drum  and  fasten  it  at  highest 
point  on  kA^mograph.  Arrange  to  turn  it  by  hand.  Fasten 
the  heavier  muscle  lever,  with  supporting  screw  down,  on 
long  stand  at  such  height  that  it  will  write  2  cm.  from 
bottom  of  drum.  Put  T  rod  on  stand  above  lever;  put 
elastic  band  on  rod ;  and  connect  band  with  lever  by  a 
thread  put  through  second  hole,  so  that  band  will  be  slightly 
stretched.  Fasten  one  end  of  a  thread  to  the  strip  of  wood 
provided,  by  passing  thread  through  hole  nearest  the  end 
and  back  through  other  hole,  and  tying  it  so  that  thread 
will  not  slip.  Fasten  other  end  of  thread  to  third  hole  in 
lever,  leaving  thread  of  such  length  that  the  end  of  the 
piece  of  wood  to  which  thread  is  fastened  will  be  so  near 
the  table  that  when  it  is  pressed  on  by  finger  the  lever 
will  move  about  4  mm.  Bring  writing  point  of  lever  to 
drum.  Mount  fork  on  short  stand,  and  place  this  stand 
so  that  fork  will  write  the  time  one  centimeter  below  lever 

and  in  same  vertical  line. 

Experiment. — The  subject 
is  to  put  finger  on  strip  of  wood 
and  depress  it  so  that  the  lever 
is  pulled  down  and  the  wood 
rests  on  table ;  ( see  that  the 
thread  is  vertical).  He  is  to 
remove  finger  as  soon  as  he  can 
after  hearing  sound  of  fork.  He 
must  not  react  to  sound  of  the 
moving  drum,  and  to  give  quick 
response  must  have  in  mind  the 
sound  of  fork.  The  experi- 
menter must  put  yoke  on  fork ; 
tell  subject  to  close  eyes;  say 
"ready,  "  and  sometimes  about  a 


>= 


Si, 


IL^ 


Fig.  26.  Apparatus  for  record- 
ing reaction  time  for  sound.  A, 
rubber  band;  B,  lever;  C,  tun- 
ing fork ;  D,  strip  of  wood, 
which  is  to  be  pressed  by  finger 
against  table. 


I20  .  EXPERIMENT  XXIV. 

second  later,  at  other  times  2  or  3  seconds  later,  whirl  the 
drum ;  then  pull  yoke  off  fork  and  stop  drum  as  soon  as 
subject  is  seen  to  respond.  Be  sure  the  drum  is  well  under 
way  before  pulling  off  the  yoke. 

Rehearse  the  experiment  two  or  three  times  without 
the  pointers  touching  the  drum.  Then  move  drum  up  to 
pointers  and  see  that  they  write  well.  Mark  the  relative 
position  of  the  pointers  on  the  drum  by  moving  them.  This 
is  to  be  done  before  each  test.  Take  10  reaction  times  with 
each  student  as  subject. 

Reading  of  Curves. — Using  two  triangles  draw  a  per- 
pendicular from  point  where  lever  began  to  move,  through 
the  corresponding  tuning-fork  curve.  Allowing  for  po- 
sition of  the  writing  points,  count  the  number  of  waves, 
starting  with  the  crest  of  the  first  and  estimating  in  tenths 
the  value  of  any  fraction  of  a  wave  at  the  end.  State  time 
in  hundredths  of  a  second.  Give  in  notes  result  of  the 
separate  observations  and  the  average  of  10  observations. 
Throw  out  only  such  observations  as  were  known  to  be 
faulty  at  the  time  they  were  made.     Account  for  variations. 

Ordinary  reaction  time  to  sound  is  0.15  second; 
to  a  touch  on  the  skin,  0.145  second;  and  to  an  electric 
flash  0.195  second. 


REACTION   time;   to   sound.  121 


122 


IvXr'I'RIMF.NT  XXIV. 


SENSATIONS.  123 

EXPERIMENT  XXV. 
Cutaneous  Sensations  and  Muscle  Sense. 

Five  types  of  sensation  can  be  obtained  from  the  sense 
organs  which  lie  close  to-  the  surface  of  the  human  skin, 
viz. :  cold,  warmth,  pressure,  tickle,  and  pain.  Each  of 
these  is  caused  by  the  excitation  of  special  spots  on  the 
skin,  and  presumably  special  types  of  nerve  endings.  The 
pressure  and  tickle  spots  appear  to  be  excited  only  by  me- 
chanical stimuli ;  the  spots  for  cold  and  warmth  are  not  so 
excited,  the  warmth  spots  responding  to  heat,  and  not  to 
cold,  and  the  cold  spots  to  cold,  and  not  to  heat.  The  pain 
spots  are  excited  apparently  most  readily  by  some  form  of 
pressure,  but  also  respond  tO'  intense  heat  and  cold. 

It  is  strange  that  the  same  form  of  mechanical  excita- 
tion, that  caused  by  the  pressure  of  the  point  of  a  small  in- 
strument, can  awaken  three  different  types  of  sensation. 
The  quality  of  these  sensations,  if  they  are  at  all  strong  is 
so  different,  however,  that  they  are  unmistakable.  The 
irritability  of  the  tickle  points  is  very  variable.  When  it 
is  slight  and  the  stimulus  is  weak,  the  sensation  is  to  be  dis- 
tinguished from  pressure,  in  that  it  is  mbre  vivid,  fixes  the 
attention  more  readily,  and  lasts  longer;  when  the  irri- 
tability is  greater,  the  tickle  sensation  is  very  diflferent  from 
the  dull,  short  lived,  pressure  sensation.  The  peculiar  burn- 
ing, or  tingling  quality,  lasting  for  a  long  time  and  often 
increasing  in  intensity  after  the  irritant  has  been  removed, 
is  suggestive  of  pain  rather  than  pressure.  It  excites  an 
almost  irresistable  desire  to  rub  or  scratch  the  place,  and 
is  inhibited  by  strong  deep  pressure  on  the  skin.  The  inhi- 
bition is  probably  due  to  fatigue.  When  the  surface  of  the 
skin  is  at  all  dry,  even  slight  pressures  cause  depression  of  a 
considerable  amount  of  surface,  and  frequently  excite  both 
pressure  and  tickle  spots  at  the  same  time,  giving  mixed 
effects.  Touch  is  probably  a  mixture  of  faint  tickle  and 
pressure  sensations.    Apparently  the  sense  organs  for  tickle 


124  EIXPKRIMENT    XXV. 

lie  slightly  more  superficial  than  those  for  pressure,  and 
the  organs  for  pain  deeper,  so  tickle  can  be  awakened 
by  the  most  delicate  pressures,  a  sensation  of  pressure  by 
slightly  stronger  pressures,  and  pain  by  still  stronger  pres- 
sures. Pressure  spots  are  closely  related  to  the  hair  follicles, 
lying  to  the  windward  side  of  the  hairs,  and  are  easily  ex- 
cited by  movements  of  the  hairs.  Tickle,  too,  can  often  be 
produced  by  very  delicate  movements  of  hairs,  but  if  the 
hairs  be  repeatedly  moved,  the  tickle  sensation  often  gives 
place  to  pressure,  because  when  the  irritability  of  the  tickle 
sense  organs  is  slight,  they  fatigue  more  rapidly  than  the 
pressure  organs.  Both  sensations  can  be  obtained  from 
parts  of  the  skin  where  there  are  no  hairs.  Pain  spots  are 
by  far  the  most  numerous,  the  tickle  spots  come,  perhaps, 
next  in  order,  then  follow  pressure,  cold  and  warmth  spots. 
The  number  of  the  different  spots  to  be  found  in  a  given 
area  of  skin  differs  greatly  in  different  parts  of  the  body. 
The  tickle  sense  organs  are  probably  our  chief  defense 
against  insects,  the  bites  of  which  have  been  found  to  in- 
noculate  animals  with  many  forms  of  disease. 

Experiment. 
a.     Cold  and  Warmth  Spots. 

Mark  with  red  ink  on  some  part  of  the  skin,  free  from 
hairs,  and  convenient  for  study,  as  the  volar  surface  of  the 
forearm,  or  the  radial  side  of  the  back  of  the  hand,  a  square. 
2x2  cm.  and  divide  this  into  four,  and  then  into  i6  squares, 
by  drawing  fine  lines.  Determine  on  yourself  the  cold  and 
warmth  spots  in  the  large  square,  by  gently  sliding  the 
rounded  point  of  a  metal  rod  forward  and  back  across  the 
surface,  in  such  a  way  as  to  cover  it  completely.  In  seeking 
the  cold  spots,  use  a  cold  dry  rod ;  and  in  trying  to  find  the 
warmth  spots,  use  a  dry  rod  that  has  been  heated  in  water 
that  feels  hot  to  the  hand.  As  the  rods  cool  quite  quickly, 
let  one  be  heating  while  the  other  is  being  used.  Mark  the 
position  of  the  spots  foimd,  by  fine  blue  and  red  crosses, 
the  ink  being  applied  by  a  fine  pointed  stick.  See  if  the  cold 
spots  respond  to  heat,  and  the  warmth  spots  to  cold.  Do 
they  react  to  pressure? 


SENSATIONS.  1 25 

b.  Tickle  and  Pressure  Spots. 

Examine:  the  skin  for  tickle  spots  in  an  area 
[  cm.  square,  by  sliding-  across  it  the  little  glass  ball 
on  the  point  of  a  fine  needle  carried  in  the  frame  which 
will  be  provided.  AVhen  a  tickle  spot  has  been  approxi- 
mately located,  determine  its  position  more  exactly 
by  reversing  the  frame  and  lightly  touching  the  skin  with 
the  head  of  the  needle.  The  pressure  spots  can  be  similarly 
located  by  using  a  slightly  heavier  needle.  If  the  skin  be  dry 
at  the  time,  exact  localization  is  impossible  because  too  large 
an  area  will  be  depressed.  Softening  the  skin  with  warm 
water  and  then  with  vaseline  is  of  assistance.  The  irri- 
tability of  the  tickle  spots  varies  greatly,  not  only  with 
different  individuals  but  by  the  same  person  at  different 
times.  Mark  the  points  found  with  fine  red  and  blue  dots. 
Is  tickle  obtained  from  the  pressure  spots,  and  vice  versa  ? 

c.  Pain  Spots. 

The  pain  spots  are  so  numerous  that  their  positions 
cannot  be  marked  except  by  very  fine  points,  and  by 
working  under  a  magnifying  glass.  I,ocate  a  number  of 
them  near  together,  and  see  whether  there  are  places  on  the 
skin  between  them  where  pain  is  not  felt.  Use  the  point 
of  a  fine  needle;  lightly  press  on  the  skin  without  punctur- 
ing it. 

Before  writing  up  your  notes,  check  up  a  number  of 
your  results,  to  see  whether  the  spots  can  be  found  a  second 
time,  at  the  place  where  they  were  first  located.  A  map  is 
to  be  drawn  showing  the  position  of  the  spots  which  were 
located. 

d.  Muscle  Sense. 

Under  this  term  are  grouped  the  sensations  supplied 
by  the  dififerent  nerves  from  the  muscles,  tendons  and  joint 
surfaces.  Although  these  sensations  are  ordinarily  un- 
noticed they  are  the  indispensable  guides  for  all  coordi- 
nated acts,  being  assisted  by  sensations  from  the  skin. 

ExP£;RiMr;NT. — i.  Close  the  eyes;  slightly  separate  one 
upper  arm  from  the  body;  flex  the  elbow  to  slightly  more 


126  e:XPSRIMENT   XXV. 

than  a  right  angle ;  partly  separate  the  fingers.  Now,  with- 
out looking,  place  the  other  arm  and  hand  in  the  same  po- 
sition. See  how  nearly  the  positions  correspond.  Repeat, 
and  closely  observe  the  sensations  which  you  experience. 

2.  Close  the  eyes ;  raise  both  arms  at  the  same  time, 
and  try  to  touch  corresponding  points  on  the  twO'  sides  of 
the  nose  at  the  same  time,  with  the  fore  fingers. 

3.  Place  the  left  hand  on  the  right;  press  down  hard 
on  the  right  hand,  at  the  same  time  that  the  right  hand  re- 
sists the  pressure.  Notice  all  the  points  where  you  experi- 
ence sensations. 

Report  the  results  of  the  above  experiments  in  your 
notes. 


SENSATIONS.  1 27 


128 


F.xpr.RiMRNT  :xxv. 


TI-IE   KNJiE-JERK. 


129 


EXPERIMENT  XXVI. 

The  Knee-jerk  as  Modified  by  Reenforcing  and  Inhibit- 
ing Influences. 

If  a  blow  be  struck  on  the  ligamentum  patellae  when  the 
lower  leg  is  in  a  position  that  puts  the  ligament  under  slight 


Fig.  27.  Diagram  of  nervous  paths  followed  by  the  nerve  impulses  causing 
tlie  knee-jerk  and  its  reenforcements.  A,  hammer  placed  to  strike  ligamentum 
patellae  ;  B,  quadriceps  muscle  ;  C,  posterior  spinal  nerve  root ;  D,  motor  cell  in 
anterior  horn  of  gray  matter  of  lumbar  cord;  E,  anterior  spinal  nerve  root;  F, 
sensory  nerve  from  other  leg;  G,  commisural  cell;  H,  descending  path  from  leg 
area  in  cerebral  cortex;  I,  descending  path  from  arm  area  in  cerebral  cortex; 
J,  motor  nerve  to  arm. 


130  EXPERIMENT  XXVI. 

tension,  a  twitch  is  transmitted  to  the  vastus  internus  and 
crureus  divisions  of  the  quadriceps  extensor  muscle.  The 
result  is  a  brief  contraction  of  this  muscle  and  a  sudden 
forward  swing  of  the  leg". 

Two  explanations  of  the  contraction  of  the  quadriceps 
are  offered;  viz:  (i)  The  knee-jerk  is  a  reflex  act  (See 
Fig.  2']')..  The  twitch  acts  as  a  mechanical  stimulus  to  the 
sensory  nerve  ends  in  the  muscle  and  its  tendon ;  the  result- 
ing impulse  passes  to  the  spinal  cord  through  the  posterior 
spinal  nerve  roots,  and  excites  anterior  horn  cells  in  the 
leg  areas  of  the  third  and  fourth  lumbar  segments  of  the 
cord ;  and  these  cells  discharge  motor  impulses  to  the  quad- 
riceps muscle  and  cause  it  to  give  a  sudden,  brief  contrac- 
tion. The  response  of  these  cells  to  the  sensory  stimulus 
may  be  either  reenforced  or  inhibited  by  other  impulses 
reaching  them  a  short  time  before  the  impulses  from  the  leg. 
(2)  The  knee-jerk  is  the  result  of  the  direct  mechanical 
stimulation  of  the  muscle,  itself.  The  greater  the  tension 
the  better  the  muscle  responds  to  the  blow  on  the  tendon. 
The  anterior  horn  cells  are  always,  during  waking  hours, 
sending  tonus  impulses  to  the  muscles  which  keep  them 
under  more  or  less  tension,  and  these  impulses  are  increased 
by  reenforcing  and  decreased  by  inhibiting  influences.  It 
will  be  here  assumed  that  the  first  explanation  is  correct. 

Apparatus  and  Position  oe  Subject. — The  subject  is 
to  lie  on  his  left  side  with  his  head  on  a  pillow,  his  thigh 
on  a  support,  and  his  foot  in  a  swing  (see  Fig.  28).  The 
position  must  be  perfectly  comfortable,  so  that  he  could 
go  to  sleep.  Adjust  the  support  (A)  under  the  thigh  so 
that  the  lower  leg  will  siving  freely.  The  subject  must  be 
in  such  a  position  that  the  cord  suspending  the  swing  is 
vertical  when  the  leg  is  at  rest ;  and  throughout  the  work 
he  must  lie  quietly  and  relaxed  with  eyes  closed  except  when 
told  do  otherwise.  Connect  the  back  of  the  swing  by  a 
thread  passing  round  pulley  (B)  to  a  cross  shaped  writing 
needle  (C),  so  that  the  rubber  band  (D)  supporting  the 
latter  is  under  a  slight  tension  and  the  needle  free  to  move. 
The  rubber  band  must  be  given  a  few  twists,  so  that  by  its 
torsion  it  will  keep  the  writing  point  against  the  drum.  Ad- 
just the  hammer  (E)  so  that  when  it  hangs  vertically,  the 


THU   KNKE-JF.RK. 


131 


middle  of  the  striking  face  will  just  touch  the  skin  over  the 
middle  of  the  ligamentum  patellae,  and  so  that  the  blow  will 
be  struck  at  right  angles  to  the  ligament.  Ordiiiarv  clothing 
will  not  interfere  with  results.  Make  this  adjustment  with 
great  care,  then  clamp  the  rod  supporting  the  hammer. 


Fig.  28.  Method  of  supporting  thigh  and  foot  and  of  recording  the  swing  of 
the  lower  leg  in  the  knee-jerk  experiment.  A,  support  under  thigh  ;  B,  pulley  ; 
C,  cross  shaped  writing  needle  ;  D,  rubber  band,  twisted  so  as  to  keep  point  of 
needle  against  drum;  'E,,  knee-jerk  hammer. 

Experiment. — Four  students  work  together,  each  taking 
his  turn  as  subject,  experimenter,  assistant,  and  clerk.  The 
experimenter  uses  the  hammer ;  the  assistant  sits  near  the 
head  ot  the  subject  and  applies  the  sensory  or  psychic 
stimuli  when  signaled  by  the  experimenter;  the  clerk  looks 
after  the  drum,  and  keeps  record  of  any  reenforcing  or 
inhibiting  stimuli,  marking  on  the  drum,  i,  2,  3,  etc.,  to  cor- 
respond to  his  notes.  During  the  entire  experiment  the 
subject  must  be  completely  relaxed  and  the  room  perfectly 
quiet.  Success  depends  entirely  on  the  contrast  between 
repose  and  action  of  the  central  nervous  system.  If  those 
who  make  the  experiment  are  not  cjuiet  and  annoy  or  excite 
the  subject,  except  when  a  special  effect  is  desired,  the 
whole  experiment  fails. 


132  EXPERIMENT  XXVr. 

a.     Record  of  Normal  Knee-Jerk. 

Find  the  position  of  the  hammer  that  will  give  a  knee- 
jerk,  the  record  of  which  is  about  2  cm.  high.  Make  note  of 
position  of  arm  holding  hammer.  Start  drum  at  2  or  3 
mm.  per  second  and  record  a  series  of  20  normal  knee-jerks, 
giving  the  blows  rythmically  at  such  a  rate  that  the  foot  has 
time  to  come  to  rest  after  each  jerk.  Observe  that  even 
when  the  subject  is  relax-ed  and  the  room  quiet,  the  knee- 
jerks  vary  in  height,  in  other  words,  that  the  irritability  of 
the  reflex  mechanism  is  changing". 

It  not  infrequently  happens,  at  first,  with  an  irritable 
subject,  that  the  writing  point  does  not  return  to  the  base- 
line, because  of  increased  tonus  of  the  extensors  of  the 
thigh.  As  he  becomes  accustomed  to  the  experiment  and 
quiets  down,  the  tonus  generally  decreases  and  the  knee- 
jerk  lessens. 

h.     Motor  Reenforcement. 

When  the  jerks  become  about  the  same  height,  zvhile 
continuing  to  strike  the  knee  rythmically,  tell  the  subject 
to  clench  his  hand  at  the  instant  the  command  is  given. 
Note  whether  speaking  to  him  causes  larger  knee-jerks,  i.  e., 
a  psychic  reenforcement;  then  give  order  to  clench  the 
hand,  and  release  the  hammer  just  after  the  order  is  given, 
i.  e.,  allow  for  reaction  time  of  subject,  and  cause  hammer 
to  strike  knee  about  o.i  sec.  after  his  hand  is  clenched.  Bow- 
ditch  and  Warren  found  that  if  the  blow  on  the  knee  occurs 
at  the  instant  the  hand  is  clenched  or  within  0.4  sees, 
after  the  clench,  the  knee-jerk  is  greater  than  normal,  i.  e. 
reenforced;  if  the  blow  is  struck  between  0.4  and  1.7  sees, 
after  the  clench,  the  knee-jerk  is  lessened,  i.  e.  inhibited. 
If  the  blow  comes  still  later,  the  clench  has  no  effect.  The 
explanation  of  the  effect  of  the  clench,  is  that  when  the 
motor-cells  of  the  arm  area  of  the  cerebral  cortex  are 
called  into  action,  the  motor  cells  of  the  leg  area  of  the 
cerebral  cortex  are  excited  through  association  fibers,  and 
impulses  from  the  cells  of  the  leg  area  of  the  cortex  spread 
to  the  anterior  horn  cells  of  the  leg  area  of  the  cord,  and 
increase  their  irritability  for  a  short  time.     If,  however,  the 


THE    KNEE-JERK.  133 

nerve  impulse  from  the  leg  reaches  the  anterior  horn  cells 
as  late  as  from  o.z]. — 1.7  sees,  after  the  clench,  it  finds  them 
in  a  condition  of  decreased  irritability,  an  after  fatigue 
effect,  and  the  knee-jerk  is  inhibited  instead  of  reenforced. 
Record  another  series  of  normal  knee-jerks,  and  see  if  the 
time  of  the  blow  with  respect  to  the  clench  alters  the  result. 
Sudden  discharge  of  voluntary  impulses  to  any  other  mus- 
cles, e.  g.  clenching  the  jaw,  or  even  winking,  will  also  cause 
a  reenforcement  or  inhibition. 

c.  Reeforcemeiit  by  Sensory  Stimuli. 

Pulling  hair,  tickling  face  with  a  camel's  hair  brush,  an 
unexpected  sound  or  odor,  an  excitation  of  the  mucous  mem- 
brane of  the  throat,  of  a  type  to  cause  unintentional,  as  well 
as  intentional  swallowing,  in  short,  any  sensory  impulse  of 
a  type  to  cause  reflex  contraction  of  voluntary  muscles,  will 
cause  a  reenforcement.  In  such  cases  the  secondary  im- 
pulse acts  to  alter  the  irritability  of  the  anterior  horn  cells 
(see  Fig.  2y) ,  and  so  effect  the  way  they  will  react  to  the 
sensory  impulses  caused  by  the  blow. 

To  show  this,  record  ten  or  more  normal  knee-jerks  by 
a  series  of  rythmical  strokes,  and  when  the  jerks  are  of 
about  equal  height,  test  several  sensory  effects,  marking  on 
drum  the  times  that  each  of  the  stimuli  is  given. 

d.  Psychic  Reenforcement. 

With  subject  as  quiet  as  possible,  eyes  closed,  room  per- 
fectly still,  record  a  series  of  10  or  more  normal  jerks,  and 
then,  while  continuing  to  strike  the  blows  rhythmically, 
test  the  effect  (i)  of  speaking  to  subject;  (2)  of  ask- 
ing him  to  multiply  two^  numbers  given  him;  (3)  of 
asking  him  to  think  of  some  stirring  poem,  etc.  The 
clerk  should  note  all  these  occurrences  with  care,  and  also 
the  effect  of  sounds  produced  in  neighboring  rooms  or 
out  of  doors,  the  entrance  of  anv  one  into  the  room,  and  all 
external  influences  that  are  able  to  excite  the  subject  in 
the  least  ■  degree.  The  susceptibility  to  such  influences 
varies  greatly  with  the  subject.  The  student  who  was  the 
subject  of  the  experiment  is  to  have  the  record. 


134  EXPERIMENT  XXVI. 


THE   KNEK-JERK. 


135 


136  EXPERIMEJNT  XXVI. 


CONDITIONS  DETERMINING  BI.OOD  PRESSURli. 


137 


EXPERIMENT  XXVII. 

Conditions   Governing   Blood  Pressure   and   Velocity   of 
Flow.    Use  of  the  Artificial  Circulation  Apparatus. 


In  this  apparatus  the  auricle  is  not  contractile,  and  the 
ventricle  is  filled  in  part  by  gravity  and  in  part  by  suction 
from  the  bulb,  which  has  a  much  greater  suction  power  than 
a  true  ventricle.    The  pulmonary  circulation  does  not  appear. 


Fig.  29.  Floor  plan  of  artificial  circulation  apparatus.  A,  bottle  representing 
left  auricle,  with  two  tubes,  representing  veins,  entering  top,  and  tube  com- 
municating with  valve  at  bottom ;  M,  mitral  valve,  consisting  of  an  aluminum 
tube,  closed  at  the  end,  and  having  a  hole  in  the  side,  which  is  covered  by  a 
tube  of  rubber  dam,  which  has  at  one  side  an  opening  for  escape  of  fluid, 
(when  the  valve  is  competent  the  rubber  tube  is  adjusted  so  that  it  covers  the 
hole  in  the  aluminum  tube,  and  when  it  is  made  incompetent  the  rubber  tube  is 
turned  round  so  that  it  only  partly  covers  the  hole  in  the  aluminum  tube).  V, 
hinged  board  actuated  by  cam,  not  shown  in  diagram,  and  compressing  the 
rubber  bulb  which  represents  the  left  ventricle ;  S,  aortic  semilunar  valve ; 
Art,  large  artery  connecting  by  Y  tube  with  two  small  arteries;  i,  screw 
clamp,  representing  muscles  in  walls  of  renal  artery ;  2,  clamp,  representing 
muscles  in  walls  of  arteries  of  skin ;  C,  tube  containing  glass  wool,  represent- 
ing resistance  in  renal  capillaries ;  RV,  renal  vein ;  SV,  skin  veins ;  3,  clamp 
controlling  mercury  manometer  recording  pressure  in  renal  artery ;  4,  clamp, 
controlling  mercury  manometer  recording  pressure  in  renal  vein;  5,  clamp 
controlling  tube  leading  to  membrane-manometer,  recording  pressure  in 
ventricle ;  6,  clamp  by  which  tube  leading  to  mitral  or  aortic  valve  can  be 
partly  closed  off  to  produce  the  resistance  of  stenosis  ;  R,  support  for  vertical 
rod,  to  which  is  to  be  clamped  the  receiving  tambour,  which  is  to  be  applied 
to  the  large  artery,  so  that  its  pulsations  may  be  recorded ;  T,  stiff  walled 
tube  which  is  to  connect  valve  chamber  S,  with  Y  tube,  when  the  effect  of  a 
stiff  walled  artery  is  to  be  studied. 

Become  thoroughly  familiar  with  the  apparatus  before 
proceeding  with  the  experiment.  Adjust  the  machine  as 
follows : 

See  that  the  clamps  3,  4  and  5,  controlling  the  connections 
with  the  manometers,  are  closed,  and  the  clamps  i  and  2, 


138  EXPlvRlMENT  XXVII. 

controlling  the  small  arteries,  are  open ;  then  fill  the  tubes 
with  water  by  pumping  rhythmically.  If  there  is  not  suffi- 
cient water  in  the  reservoir,  have  the  assistant  replenish  it 
with  distilled  water.  When  fi,lling  the  tubes,  hold  the  right 
hand  end  of  the  apparatus  up  at  an  angle  of  45°,  until  the 
air  is  out  of  the  tubes  nearest  the  bulb,  and  then  tip  up  the 
other  end,  and  expel  the  air  from  the  rest  of  the  tubes. 

Compress  the  bulb  only  by  means  of  the  board  placed 
above  it.  The  rod  supporting  the  cam  can  be  moved  up 
or  down.  When  a  small  amount  of  compression  is  desired, 
let  the  end  of  the  rod  rest  on  the  little  block  of  wood  be- 
neath ;  when  more  compression  is  needed,  swing  the  block 
to  one  side  and  lower  the  rod. 

The  folloiving  cautions  must  he  observed. 

The  air  should  be  driven  out  of  the  apparatus. 

The  arterial  manometer  should  be  watched,  to-  see  that 
the  mercury  is  not  driven  down  round  the  bottom  of  the  U. 

The  clamps  controlling  at  least  one  of  the  arteries  should 
be  kept  partly  open  ;  see  that  during  the  pumping  water 
flows  into  the  reservoir. 

Be  careful  not  to  bend  the  rods  carrying  the  pointers  of 
the  mercury  manometer. 

Mercury  should  not  be  allowed  to  collect  above  the  mano- 
meter floats. 

Dry  the  apparatus  and  table  before  leaving,  and  raise  the 
rod  so  that  the  board  shall  not  rest  on  the  bulb. 

Whenever  the  stopper  is  to  be  taken  out  of  a  valve 
chamber,  clamp  the  tube  between  the  bottle  and  the  mitral 
valve. 

ADJUSTMENT   01'   APPARATUS. 

Connect  the  arterial  and  venous  system  of  the  apparatus 
with  the  larger  and  smaller  manometers,  respectively,  and 
open  the  clamps  wide.  Mount  a  time  signal  to  write  at 
the  bottom  of  the  curve,  about  half  a  centimeter  below  the 
venous  manometer.  Adjust  the  pointers  on  the  floats  so 
that  the  venous  manometer  will  write  about  a  centimeter 
below  the  arterial ;  the  three  writing  points  should  be  in  the 


CONDITIONS  DEJTe:EMINING  BLOOD  PRESSURE.  1 39 

same  vertical  line.  Be  very  careful  not  to  bend  the  delicate 
rods  carrying  the  pointers. 

Adjust  the  apparatus  to  what  may  be  called  "normal" 
conditions. 

a.  By  sliding  the  piece  of  wood  under  the  rod  on  which 
the  cam  operates,  thus  limiting  the  compression  of  the 
bulb,  and  the  amount  of  fluid  pumped. 

b.  By  screwing  down  clamp  2  on  the  tube  not  connected 
with  the  capillaries. 

c.  By  gradually  tightening  the  other  arterial  clamp  i, 
until  •  the  flow  into  the  bottle  is  constant  and  the  venous 
manometer  barely  oscillates,  and  the  arterial  manometer 
records  a  diastolic  pressure  of  about  25  mm.  (i.  e.,  the  pointer 
keeps  about  12^  mm.  above  the  base  line  at  the  close  of 
diastole)  when  the  rate  of  pumping  is  once  in  two  seconds. 

Pump  rhythmically  at  the  rate  of  once  in  two  seconds, 
and  obser\'e : — 

1.  The  ventricle  is  filled  mainly  by  the  suction  created 
during  diastole,  and  partly  by  the  force  of  gravity.  (In  the 
body  suction  plays  only  a  small  part,  the  ventricle  being 
filled  by  the  returning  blood  and  by  the  contraction  of  the 
auricle.) 

2.  The  force  of  the  ventricular  contraction  is  converted 
partly  into  energy  of  flow,  i.  e.,  kinetic  energy,  as  seen  by 
the  entrance  of  the  fluid  into  the  bottle;  and  partly  into  en- 
ergy of  pressure,  i.  e.,  potential  energy,  as  seen  by  the 
stretching  of  the  wall  of  the  large  artery,  and  the  rise  of  the 
mercury  in  the  manometer. 

3.  The  pressure  falls  during  diastole,  because  the  po- 
tential, or  pressure,  energy  is  converted  into  energy  of 
flow,  as  shown  by  the  venous  flow,  the  narrowing  of  the 
large  artery,  and  the  fall  of  the  mercur}^  in  the  arterial  man- 
ometer. 

4.  The  pressure  in  the  veins  is  low,  because  of  the 
small  resistance  ahead,  and  the  fact  that  a  large  part  of  the 
energy  is  expended  in  overcoming  the  resistance  in  the 
small  arteries. 


140  EXPERIMENT  XXVII. 

5.  The  pressure  in  the  veins  is  quite  constant,  because 
it  is  kept  up  during  systole  by  the  contraction  of  the  ven- 
tricle, and  during  diastole  by  the  elastic  recoil  of  the  arterial 
walls  acting  against  the  resistance  in  the  small  arteries  and 
capillaries.  Notice  that  if  the  resistance  is  lessened  by 
opening  clamp  i  on  the  artery  connected  with  the  capillaries 
(causing  vaso-dilation),  the  flow  becomes  rhythmic,  and  that 
as  this  clamp  is  screwed  down  (vaso-constriction  produced), 
the  venous  flow  becomes  constant  again,  and  the  venous 
manometer  ceases  to  oscillate.  Adjust  the  arterial  clamp  so 
that  the  venous  manometer  bearly  oscillates,  and  make  the 
following  experiments: 

EXPERIMENTS.     PART  I. 

a.     Effect  of  Inertia  of  Mercury. 

Adjust  the  drum  to  the  pointers,  and  revolve  it  to  draw 
base  lines.  Pump  for  twenty  seconds  at  a  regular  rate  of 
once  in  two  seconds,  watching  the  venous  flow  and  the 
arterial  manometer,  and  when  the  rhythm  has  been  acquired, 
and  the  mercury  has  reached  the  new  level,  continuing  at  the 
same  rate,  start  the  drum  and  take  a  record.  The  venous 
pressure  remains  almost  constant  and  low ;  the  arterial 
pressure  rises  in  systole,  and  during  diastole  gives  several 
oscillations,  due  to  the  inertia  of  the  mercury. 

Now  gradually  screw  down  the  clamp  3  on  the  tube 
communicating  with  the  arterial  manometer  until  these  sec- 
ondary oscillations  disappear.  Leave  the  machine  adjusted 
in  this  wav  in  the  following  experiments.  This  method  is. 
used  to  minimize  the  changes  due  to  inertia,  and  gives  a 
record  approaching  more  nearly  the  mean  pressure. 

h.     Effect  of  Rate. 

Pump  at  the  rate  of  once  in  two  seconds  and  when  the 
arterial  pressure  has  reached  the  new  level,  start  the  drum 
and  record  five  or  six  pressure  waves  and  stop  drum.  Re- 
peat at  the  rate  of  once  a  second,  and  again,  at  a  rate  of  once 
in  two  seconds.  Next  decrease  rate  to  once  in  three  seconds, 
and  record  five  waves. 


CONDITIONS  DF,Ti;RMINING  BLOOD  PRESSURE.  I4I 

c.  Effect  of  Increased  Output.    . 

Pump  at  a  rate  of  once  in  two  seconds,  and  when  the 
pressure  has  reached  the  new  level,  start  the  drum  and 
record  five  waves.  Now  increase  the  output  by  lowering  the 
rod  on  which  the  cam  works,  and  repeat,  recording  five 
waves. 

d.  Effect  of  Resistance. 

Pump  with  ^'normal  output,"  at  the  rate  of  once  in  two 
seconds ;  when  the  pressure  level  is  reached,  record  five 
waves  and  stop  the  drum ;  keep  on  pumping,  but  loosen  the 
screw  of  clamp  i,  representing  the  peripheral  arterioles,  and 
when  the  new  pressure  level  is  reached,  start  the  drum  and 
record  five  waves;  stop  the  drum,  but  keep  on  pumping; 
now  screw  down  the  clamp  until  the  venous  flow  is  almost 
obliterated,  and  when  the  new  pressure  level  is  reached, 
start  the  drum  and  record  five  waves. 

e.-   Effect  of  Resistance   in    Tivo  Systems  of  Arteries  on 
Distribution. 

The  main  artery  divides  into  two  branches;  the  one 
having  the  capillaries  and  controlled  by  clamp  i,  can  be  con- 
sidered the  renal  artery,  and  the  other  controlled  by  clamp 
2,  the  arteries  of  the  skin.  Dilation  of  the  skin  vessels  will 
lower  the  general  arterial  pressure,  and  the  pressure  in  the 
renal  artery  Avill  fall,  and  the  flow  through  the  kidney  will 
lessen.  Increasing  the  vaso-constriction  in  the  skin  will 
produce  the  opposite  efi^ect. 

Test  this  out  on  the  model,  by  pumping  at  the  rate  of 
once  in  two  seconds,  when  clamp  i  is  adjusted  to  "normal 
conditions,  and  clamp  2  is  closed ;  then  while  continuing  to 
pump,  and  while  watching  the  flow  from  the  renal  vein,  grad- 
ually open  clamp  2,  (produce  vaso-dilation  in  the  skin  ves- 
sels) ;  then  screw  dowm  clamp  2,  (cause  vaso-contriction  in 
the  skin).  Repeat  the  experiment  with  the  drum  running, 
and  record  the  changes  in  pressure  in  the  renal  arten'. 


142  i:xpt]:rime;nt  xxvii. 

/.     Some  Clinical  Applications. 

By  varying  the  rate  of  pumping-,  the  volume  pumped, 
and  the  peripheral  resistance,  one  can  imitate  a  number  of 
interesting  phenomena. 

1.  Hffect  of  Vagus  Inhibition.  By  vagus  inhibition  the 
heart  is  stopped,  then  occasional  beats  are  seen,  then,  when 
the  inhibition  ceases,  the  heart  beats  gradually  faster  until 
a  rate  somewhat  higher  than  normal  is  reached  (to  compen- 
sate for  the  low  pressure),  and  then  returns  to  its  normal 
rate.  To  test  these  effects,  adjust  machine  to  normal  con- 
ditions, pump  at  rate  of  once  in  two  seconds,  let  drum  run, 
and  after  about  ten  seconds  produce  the  inhibition  effects 
by  altering  the  rate  of  pumping 

2.  Action  of  Depressor  Nerve.  This  nerve  starts  at  the 
root  of  the  aorta,  where  it  is  excited  by  a  pressure  higher 
than  normal.  It  acts  to  inhibit  the  vaso- constrictor  center 
in  the  medulla  and  possibly  to  excite  the  vaso-dilator  center, 
and  so  causes  vaso-dilation.  The  action  can  be  readily  imi- 
tated by  pumping  at  a  regular  rate,  and  after  the  normal 
pressure  is  obtained,  lessening  the  peripheral  resistance  in 
the  small . arteries  gradually,  (clamp  2  can  be  used  to  ad- 
vantage), and  then  restoring  the  pressure  by  gradually 
tightening  the  clamp. 

3.  Tranbe-Hering  Wairs.  These  waves  are  caused  by 
rythmic  action  of  the  vaso-constrictor  center. 

4.  Nitrite  of  Amy  I.  This  drug  acts  on  the  muscles  of 
the  walls  of  the  arteries,  causing  them  to  dilate.  As  the 
dilation  occurs  the  heart  beat  quickens  to  compensate  for  the 
fall  of  blood  pressure.  During  the  pumping  produce  a 
gradual  fall  of  pressure,  and  then  attempt  to  restore  the 
pressure  by  cjuickening  the  rate  of  the  heart. 

5.  Hardening  of  Wall  of  Artery  (arterial  sclerosis). 
Obtain  a  "normal"  record  of  five  or  six  pressure  waves. 
Stop  the  drum,  substitute  for  the  elastic,  an  inelastic,  stiff 
walled  rubber  tube  (T)  supplied  in  the  basin.  Leaving  the 
other  adjustments  as  before,  pumping  at  the  same  rate, 
again  record  five  or  six  waves.  Observe  the  character  of  the 


CONDITIONS  DE;Tli:RMINING  BLOOD  PRESSURE. 


143 


flow  into  the  bottle.  Caution.  There  will  be  a  big  fling  of 
the  mercun^  and  the  manometer  must  be  watched  to  see  that 
the  mercury  is  not  thrown  out. 

Notes.  State  in  the  notes  the  eft'ect  of  increased  heart 
rate,  increased  output,  increased  peripheral  resistance,  and  a 
hardening  of  the  arterial  wall,  on  the  mean,  systolic,  diastolic 
and  pulse  pressures  recorded  by  the  arterial  manometer.  State 
effect  of  these  factors  on  the  venous  pressure,  on  the  size 
of  the  venous  pressure  oscillations,  and  the  venous  flow. 
State  how  the  blood  flow  through  an  organ  is  influenced  by 
vaso-motor  changes  in  a  distant  organ.  The  results  may 
be  given  to  advantage  in  tabular  form,  an  increase  being 
noted  by  -f-  and  a  decrease  by  — . 


Heart   has  Increased 

Vaso-constriction 

Artery 

Rate 

Output 

I^ocal 

Distant 

Harden- 
ed 

Arterial  pressure 

Mean 

Systolic 

Diastolic 

Pulse 
Venous  pressure 
Venous  oscillations 
Venous  flow 

144  e:xpi<:rime;nt  xxvii. 


CONDITIONS  DETERMINING  BLOOD  PRESSURE.  145 

EXPERIMENT  XXVI I—SECOND  DAY. 

PART  II. 

THe  method  of  air  transmission  devised  by  Marey,  is 
employed  to  record  a  great  variety  of  physiological  move- 
ments. By  this  method,  two  little  drums  covered  with  rub- 
ber membrane  are  connected  together  by  tubing.  A  plate  of 
metal  resting  on  the  membrane  of  one  of  the  drums,  (the 
recording  tambour),  is  connected  with  a  light  lever,  and 
wdien  air  enters  or  is  driven  out  of  the  other  drum  (the 
receiving  tambour),  by  movements  imparted  to  the  mem- 
brane covering  it,  the  lever  rises  or  falls.  There  is  a  T- 
tube  at  one  part  of  the  tubing  connecting  the  drums,  and  this 
supplies  a  side  opening  by  which  air  can  enter  or  escape 
when  the  tambours  are  not  in  use.  This  opening  is  con- 
trolled hv  a  pinch-cock.  The  level  of  the  lever  can  be  ad- 
justed by  placing  the  support  of  its  axis  at  a  suitable  angle. 

Caution.  Do  not  ap- 
ply the  pinch-cock,  ex- 
cepting when  the  tam- 
bours are  to  be  used. 
See   that   the  lever   of 

iMg.    30.     Recording   tambour.      A,    tambour;  ,.  ^ 

B,    alumimim   plate,    with   ball-and-socket   joint  the    reCOrdUlg  tamOOUr 

for  pin  acting  on  lever;   C,  lever  with  celluloid  •        Ur^rivr^-nt^]  incf     ht^- 

writing  point ;   D,   support  of  lever.  ^S     IJOriZOniai  JUSt      DC 

fore  a  record  is  to  be 
taken,  and  never  let  the  membrane  of  the  recording  tambour 
be  greatly  stretched. 

Adjustment  of  Apparatus  to  Record  the  Pidse  and 
Ivtrai'entricular   Pressure. 

Adjust  a  receiving  tambour  to  the  wall  of  the  arter}^ 
and  connect  it  with  the  large  recording  tambour.  Connect 
the  tube  from  the  ventricle  with  the  small  recording  tam- 
bour. Arrange  the  writing  points,  to  write  in  the  same 
vertical  line  with  the  float  of  the  arterial  manometer.  Adjust 


146  EXPIJRIMENT  XXVII. 

the  rod  limiting  the  pressure  of  the  cam  on  the  bulb  so  as 
to  give  a  small  output  from  the  ventricle,  then  pump  in  the 
manner  directed,  at  the  rate  of  once  in  two  seconds. 
Only  a  very  small  pulse  is  given  with  clamp  i,  represent- 
ing small  arteries,  wide  open.  Gradually  increase  the  peri- 
pheral resistance,  and  observe  the  resulting  distention  of 
large  arterv  and  pulsation  of  tambour.  Several  beats  may 
be  required  to  fill  the  artery  before  the  tambour  will  record, 
and  then  the  record  should  be  8-10  mm.  high.  Record  on 
the  drum,  simultaneously,  the  pulse,  the  intra-ventricular 
pressure,  the  arterial  and  venous  pressures,  and  the  time. 
The  pulse  given  by  the  apparatus  does  not  give  a  true  picture 
of  the  human  pulse ;  for  example  the  dicrotic  and  the  predi- 
crotic  and  postdicrotic  waves  are  not  shown.  One  can  use  the 
machine,  however,  to  study  the  effect  of  a  number  of  con- 
ditions on  the  height  of  the  pulse  oscillations,  and  on  the 
rate  of  fall  of  the  pulse  wave. 

a.  Effect  of  Rate. 

With  the  machine  adjusted  for  normal  conditions,  pump 
for  thirty  seconds,  at  the  rate  of  once  in  two  seconds ;  start 
the  drum,  adjusted  to  run  four  mm.  per  second,  and  record 
five  or  six  waves.  Stop  drum.  T'ump  at  the  rate  of  once 
a  second ;  once  in  two  seconds ;  once  in  three  seconds,  con- 
secutively, getting  records  in  each  case,  stopping  the  drum 
between  records. 

b.  Effect  of  Vohime  Output. 

Record  five  normal  waves.  Stop  drum.  Increase  output 
by  lowering  rod  and  keeping  the  same  rate,  record  five  more 
waves. 

c.  Effect  of  Peripheral  Resistance. 

Open  the  clamp  (i)  representing  the  peripheral  resist- 
ance in  the  arterioles.  Pump  at  the  rate  of  once  in  two 
seconds,  and  record  five  waves.  (Low  resistance  pulse). 
Stop  drum,  continue  pumping,  and  gradually  increase  the 


CONDITIONS  DETERMINING  BLOOD  PRESSURE.  147 

peripheral  resistance  by  tightening  the  clamp  until  a  stream 
barely  flows  into  the  bottle.  Record  five  waves.  Caution — 
Watch  arterial  manometer. 

Azotes. — B.vplain  effect  of  rate  and  volume  output  on 
shape  and  she  of  pulse.  Why  docs  increasing  peripheral 
resistance^  for  example,  cause  pulse  waves  to  first  grow 
larger  and  then  svialler?  Explain  the  effect  on  the  rate  of 
fall  of  the  pulse  wave.  Explain  difference  in  ventricular  and 
aortic  pressure  curves. 

PART  III. 

Effect  of  Lesions  of  Heart  Valves. 

Failure  of  a  valve  to  close  its  orifice  perfectly  is  called 
insuificiency.  Abnormal  narrowing  of  its  aperture  is  called 
stenosis.  These  defects  in  heart-valves  are  usually  accom- 
panied by  dilation  of  the  cavities,  which  discharge  through 
the  valves,  and  hypertrophy  of  the  heart  muscle,  which  is 
known  as  compensation.  These  three  conditions  can  be 
imitated  in  a  way  in  this  machine  as  follows :  Insuificiency, 
by  rendering  a  valve  incompetent,  by  adjusting  the  rubber 
tube  so  that  it  only  partially  covers  the  opening  in  the  alum- 
inum tube ;  stenosis,  by  applying  clamp  6  to  the  tube  leading 
to  a  valve  chamber ;  and  compensation,  b}'  increasing  the 
compression  of  the  bulb,  thus  permitting  a  greater  outflow 
at  a  stroke. 

It  must  be  borne  in  mind  that  these  lesions  in  the  living 
subject  are  accompanied  by  other  changes,  so  that  the  results 
are  of  value  only  as  indicating  fundamental  relations, 'which 
are  here  separated  from  complications  usually  present.  In 
the  model  compensatory  changes  can  occur  only  in  the  left 
ventricle,  and  the  compensator}-  effects  produced  by  changes 
in  the  auricle  and  in  the  right  side  of  the  heart  cannot  be 
studied. 

With  the  apparatus  adjusted  for  normal  conditions,  be- 
ing sure  that  there  is  a  slight  venous  pulse,  and  pumping 
at  the  rate  of  once  in  two  seconds,  record,  first,  five  or  six 


148 


EXPERIMENT  XXVII. 


normal  beats ;  stop  the  drum,  create  the  lesion  desired, 
and  after  pumping  a  number  of  times,  start  the  drum^  and 
record  five  or  six  lesion  curves.  Again  stop  the  drum, 
cause  the  compensation,  and  after  pumping  a  short  time, 
again  record  five  or  six  waves.  This  comjpares  in  a  row, 
normal  curves,  effect  of  cardiac  lesions,  and  effect  of  com- 
pensation. 

Repeat  for  each  valvular  lesion  in  the  following  order: 

a.  Mitral  Stenosis. 

b.  Aortic  Stenosis. 

c.  Mitral  Insufficiency. 

d.  Aortic  Insufficiency. 

Notes. — B.vplain  the  results  in  each  case,  and  state  in 
which  cases  the  compensation  tnade  the  curve  more  nearly 
normal,  and  zvhy.    Also  state  changes  in  form  of  pidse. 

Use  the  follozmng  form  in  reporting  the  effects  of  the 
valvular  lesions  studied. 


LESION 

PREvSSURE 
Increased  or  Decreased 

COMPENSATION 
Effective  or  Ineffective 

Mitral 
Stenosis 

vSystolic. 

Diastolic 

Pulse 

Intraventricular 

Venous 

CONDITIONS  DEITIJRMINING  BLOOD  PRESSURE).  1 49 


I50  EXPIvRIMENT  XXVIl. 


CIRCUT,ATI0N  AND  RESPIRATION  01^   MAM  MAI,. 


151 


EXPERIMENT  XXVIII. 

Circulation  and  Respiration  of  the  Mammal, 

Experiments  on  these  subjects  will  fill  two  afternoons, 
the  apparatus  and  general  methods  being  the  same  for  both 
days.  The  students  will  work  in  groups  of  four,  and  the 
part  of  the  work  to  be  done  by  each  student  is  shown  in 
the  following  schedule.  The  number  of  the  student  as 
given  in  the  schedule  will  be  assigned  by  lot. 

SCHEDULE  OF  WORK. 


Experiment  28 

Student  i 

Student    2 

Student    3 

Student  4 

Right  carotid 
and  vagus 

Operate 

Assist 

Etherize 

Apparatus 

Left  carotid 
and  vagus 

Apparatus 

Operate 

Assist 

Etherize 

Sciatic 

Etherize 

Apparatus 

Operate 

Assist 

Tracheotomy 
and  open  chest 

Assist 

Etherize 

Apparatus 

Operate 

Second  Day 
Experiment  20 

Right  carotid 
and  depressor 

Assist 

Etherize 

Apparatus 

Operate 

Left  carotid 
and  depressor 

Etherize 

Apparatus 

Operate 

Assist 

Tracheotomy 
and  open  chest 

Apparatus 

Operate 

Assist 

Etherije 

Phrenic  and 
peristalis 

Operate 

Assist 

Make  nerve 
leg  prepart'n 

Apparatus 

Success  in  the  experiments,  requires  that  the  apparatus 
shall  be  thoroughly  understood  before  the  work  is  begun. 
Students  assigned  to  this  work  will  be  given  an  opportunity 
to  study  the  apparatus,  and  be  quizzed  on  these  notes,  the 
latter  part  of  the  preceding  afternoon. 


152 


experime;nt  XXVIII. 


Apparatus. — The  arrangement  of  the  apparatus  is  to 
be  seen  in  Fig.  31.  The  following  list  of  apparatus  and 
instruments  will  be  required,  and  everything  must  be  at 
hand  before  the  work  is  begun.  The  cannulae  are  to  be  kept 
in  parafine  oil,  and  will  be  issued  by  the  Instructor. 


APPARATUS  TO  Bt  FURNISHED  BY  LABORATORY. 


Animal-board  with  head-holder. 
Manometer  outlit. 
Artificial  respiration  outfit. 
Basin  for  sodium  chloride. 
Battery  jar. 
Bottle  of  ether. 
Bulb  and  cannulae  for  artery. 
Cabinet-makers'  clamp. 
Two  Cannulae  for  trachea. 
Burette  clamp. 
Three  clamps  for  stand. 
Screw  clamp  for  trachea. 
Three  screw  clamps. 
Etherizing  cone. 
Four  cords  for  animal  board. 
Two  cords  with  hooks. 
Two  cloth  covers. 
Director. 

Dish  for  sodium  sulphate. 
Dropper. 


Electrodes. 

Bulldog  forceps. 

Kymograph  for  long  paper 

Lig'atures,  fine. 

Ligatures,  coarse. 

Water  manometer. 

Two  pinch  cocks. 

Plate. 

Pneumograph. 

Rod,  nickled. 

Rubber  tube  with  glass  T. 

Scalpel. 

Shears. 

Sponge. 

Small  stand. 

vSupport  for  kymograph. 

Recording  tambour. 

Two  towels. 

Silk  thread  and  weight. 

Time  signal. 


APPARATUS    TO    BE    F'Ui^NISIIED    BY    THE    FOUR    STUDENTS    AS- 
SIGNED TO  THE  WORK. 


One  dry  cell. 
Induction  coil. 
Drum  square. 


Fine  and  strong  forceps. 

Mercury  key. 

Wires. 


CIRCULATION  AND   RF.SPURATION   OF    MAMMAL. 


153 


DIRECTIONS    TO    STUDENTS    CARING    EOR    APPARATUS. 

First  close  cock  i  and  all  clamps,  then  raise  pressure  to 
no  mm.  (55  on  scale),  in  bottle  (I)  containing  anticoagu- 
lation fluid,  by  using  pump.  Pump  very  carefully,  or  the 
mercury  will  be  forced  out  of  the  manometer.  Next  raise 
bulb  K  until  it  and  its  tube  are  vertical ;  open  clamp  4,  then 
gradually  open  clamp  3,  and  let  fluid  rise  in  tube  and  fill 
bulb ;  finally  close  clamps  3  and  4.  Put  bulb  in  dish  so  that 
any  drip  will  be  caught.     Open  cock  i,  and  then  gradually 


Fig.  31.  Scheme  of  apparatus  for  studying  the  blood  pressure  of  a  mammal. 
A,  tambour  lever;  B,  pointer  of  a  manometer  float;  C,  time  signal;  D,  short- 
circuit  key;  E,  mercury  float;  F,  electrodes;  H,  bicycle  pump;  I,  anticoagula- 
tion tluid  pressure  bottle ;  J,  manometer  communicating  with  pressure  bottle ; 
K,  bulb  and  cannula;   i,  cock;   2,  3,  4,  clamps. 

open  clamp  3  and  fill  the  tubes  connected  with  the  mano- 
meter. When  the  fluid  has  risen  as  far  as  clamp  2,  close 
clamp  3  and  then  clamp  2  and  cock  i.  It  may  be  necessary 
to  introduce  a  vvdre  into  the  right  side  of  the  manometer 
after  taking  off  clamp  2,  in  order  to  remove  the  air  from  that 
portion  of  the  manometer.  If  in  the  process  of  filling,  air 
bubbles  are  seen  in  the  tubes,  they  may  be  removed  by  rais- 
ing the  manometer  end  of  the  system  and  tapping  on  the 
tubes.      Clamp    3    should   be   closed   or   only    slightly   open 


154  EXPERIMENT  XXVIII. 

while  this  is  being-  done.  Notice  that  the  mercury  in  the 
two  arms  of  the  manometer  is  not  at  the  same  level.  This  is 
due  to  the  weight  of  the  anticoagulation  fluid  on  one  side  of 
the  U.  Now  place  bulb  K  slightly  above  level  of  mercury 
in  manometer ;  open  cock  i  and  clamp  4,  and  lower  bulb 
until  the  mercury  of  the  recording  manometer  has  the  same 
level  in  the  two  arms ;  close  clock  i  and  clamp  4.  Place 
point  of  time  signal  (C)  just  behind  and  on  a  level  with  the 
pointer  of  the  manometer  float  (B).  The  time  record  will 
in  this  position  give  a  base  line  from  which  all  pressures 
are  to  be  read. 

Connect  the  clock  circuit  with  the  binding  posts  at  the 
back  of  the  board  connected  with  the  time  signal.  Place  the 
induction  apparatus  behind  the  manometer  outfit,  and  put  a 
dr}'  cell  and  a  key  in  the  primar)^  circuit,  connecting  them 
so  as  to  give  a  tetanizing  current.  Connect  secondary  coil 
with  the  binding  posts  at  the  back  of  the  board  connected 
with  the  short-circuit  key  (D)  on  top  of  manometer  board. 
Fasten  a  pair  of  electrodes  (P")  to  the  binding  posts  on  the 
front  of  the  board.  Start  vibrator,  open  short-circuit  key, 
and  test  current  with  the  tongue.  A  current  of  medium 
strength  will  suffice.  Using  drum  square,  see  that  writing 
points  of  recording  tambour  (A),  manometer  (B),  and  key 
(D)  write  in  the  same  vertical  line. 

By  means  of  pump,  raise  the  pressure  in  the  bottle  con-  ■ 
taining  anticoagulation  fluid  until  the  mercury  in  the  mano- 
meter connected  with  the  bottle  stands  at  100  mm.,  pumping 
with  care.  Open  cock  i,  and  then  gradually  open  clamp  3, 
until  the  mercury  in  the  recording  manometer  rises  to  50 
mm.  Close  i  and  3.  The  true  pressure  is  twice  the  amount 
recorded,  for  the  mercury  falls  on  one  side  of  the  tube  as  it 
rises  on  the  other.  The  object  of  raising  the  pressure,  is  to 
limit  the  amount  of  blood  which  will  leave  the  artery  when 
it  is  connected  with  the  manometer. 

The  apparatus  must  be  ready  to  use  the  instant. that  the 
operation  is  completed.  See  that  three  loops  of  paper  for 
kymograph  have  been  blackened,  and  place  one  on  the 
drums.  Mark  the  position  of  the  writing  points  on  the 
paper. 


CIRCULATION   AND  RESPIRATION   OF    MAMMAL-  155 

During  the  taking  of  the  records  you  must  start  and 
stop  the  drum ;  must  mark  the  position  of  the  writing  points 
on  the  dnnii  before  each  test ;  must  give  the  stimulations  by 
depressing  the  short  circuit  key ;  see  that  the  drum  runs  for 
at  least  15  seconds  before  and  15  seconds  after  each  test; 
put  a  letter  a,  b,  c,  etc.,  indicating  the  experiment,  just  over 
the  record  of  the  short  circuit  key,  for  each  test ;  and  must 
label  each  loop  of  paper  with  your  name,  before  giving  it  to 
the  assistant  to  fix.  At  the  close  of  the  experiment,  you  must 
clean  all  stimulating  and  recording  apparatus,  and  account 
for  each  piece  to  the  Instructor. 

DIRECTIONS  TO  ASSISTANT. 

It  is  the  business  of  the  assistant  to  see  that  the  instru- 
ments and  ligatures  are  in  order,  and  are  at  the  hand  of  the 
operator  throughout  the  operation  and  the  experiment.  Can- 
nulae  will  be  supplied  by  the  Instructor  when  required. 
While  the  animal  is  being  etherized,  fill  the  animal  board 
with  water  at  45°  C;  heat  some  salt  solution  in  a  basin  pro- 
vided for  the  purpose,  put  a  sponge  in  it,  and  place  it  on 
the  operating  table.  During  the  operation,  be  ready  to 
sponge  the  wound,  to  pass  needed  instruments  to  the  oper- 
ator, and  to  tie  the  ligatures  when  required.  Do  not  be 
officious.  Remember  that  you  are  the  assistant  of  the  oper- 
ator. At  the  close  of  the  experiment  you  must  return  all  in- 
struments, cannulae,  etc.,  in  good  order  to  the  Instructor, 
and  see  that  the  animal  board,  head  holder,  and  artificial 
respiration  apparatus  are  clean. 

Anesthesia. 

Anesthesia  may  be  divided  into  three  stages :  I,  Incom- 
plete ;  II,  Complete :  and  III,  Danger  period.  These  stages 
show  the  following  peculiarities,  which  must  be  kept  in 
mind  when  administering  ether.  (For  anesthesia  in  man, 
see  Cushney's  Pharmacology^) 

Stage  I.  a.  Straggling  because  of  dislike  of  the  drug, 
and  later  because  of  excitation  of  Nervous  Systems ;  respira- 
tion irregular  from  irritation  of  mucous  membrane,  often 


156 


EXPERIMF.NT  XXVIII. 


with  pauses  and  gasps  ;  salivation  for  the  same  reason ;  pupil 
dilated,  b.  Consciousness  beginning  to  he  lost,  and  toward 
end,  lessening  of  reflexes. 

Stage  II.  Quiet;  respiration  regular  and  deep,  ("snor- 
ing respiration")  ;  pupil  contracted;  reflexes  lost;  complete 
unconsciousness. 

Stage  III.  The.  danger  period.  Respiration  slow  and 
shallow,  often  long  pauses;  pulse  slow  and  feeble;  pupil 
dilating  quickly ;  absence  of  all  reflexes. 

Rabbits  difl^er  from  men,  dogs,  and  cats,  in  that  convul- 
sive respirations  immediately  precede  death  in  the  third 
stage. 

These  effects  may  be  tabulated  as  follows : 

STAGES  ANESTHESIA. 


Incompleti; 

Complete; 

Danger  Point 

Respiration 
Depth 

Medium 

Deep 

Shallow 

Rate 

Rapid 

Slow 

Slow 

Regularit}^ 

Irregular 
often  long 
pauses 

Regular 

Gasps  or  long 
pauses,  or 
convulsive 

Reflexes 

Present 

Absent 

Absent 

Pupil 

Dilated 

Contracted 

Dilating 

The  Behavior  of  the  Pupil  may  be  explained  as  follows : 
The  size  of  pupil  is  controlled  by  twO'  muscles,  the  sphincter 
pupillae  and  the  dilator  muscle.  Each  of  these  antagonists 
is  during  waking  hours  in  more  or  less  tonus.  Contrac- 
tion of  the  pupil  might  be  caused  by  excitation  of  the 
sphincter  or  inhibition  of  the  dilator  muscle ;  dilation  might 


CIRCULATION  AND  RESPIRATION  OE   MAMMAL.  157 

be  caused  by  excitation  of  the  dilator  muscle  or  inhibition  of 
the  sphincter ;  or  both  of  these  processes  might  occur  simul- 
taneously ("reciprocal  innervation"). 

During-  waking  periods,  the  tone  of  the  sphincter  tends 
to  be  inhibited  by  sensory  stimuli,  and  the  pupil  tends  to 
dilate. 

Light  falling-  on  the  retina  causes  reflex  excitation  of  the 
sphincter,  and  perhaps  inhibition  of  the  dilator,  and  the 
pupil  tends  to  contract. 

Emotional  excitement  tends  to  cause  marked  dilation  of 
the  pupil;  by  excitation  of  the  dilator,  as  well  as  inhibition  of 
the  sphincter,  and  this  is  to  be  seen  zvhen  the  ether  is  first 
applied. 

In  sleep  the  eyes  are  rolled  upward  and  outward,  and 
the  pupils  constrict  because  of  lessening  tone  of  the  dilator 
and  greater  tone  of  the  sphincter,  and  this  is  to  be  seen  in 
complete  anesthesia. 

In  the  danger  stage,  the  centers  controlling-  the  sphincter 
cease  to  act  and  the  pupil  dilates. 

Directions  to  Anesthetizer. 

vSee  that  there  is  no  gas  flame  in  the  same  part  of  the 
room.  Ether  vapor  travels  far  and  is  exceedingly  inflam- 
mable. 

Let  the  student  who  is  to  operate,  hold  the  four  legs  of 
the  rabbit  between  the  fingers  of  the  left  hand,  and  hold 
the  ears  between  the  second  and  third  fingers,  and  the  nose 
between  the  thumb  and  index  finger  of  the  right  hand.  He 
should  take  care  not  to  use  unnecessary  force.  There  is  no 
need  of  hurting  the  animal. 

The  ,anesthetizer  puts  some  ether  on  the  gauze  of  the 
cone,  and  places  the  cone  over  the  animal's  mouth  and  nose. 
It  is  well  to  place  a  towel  beneath  the  head,  and  bring  it 
up  to  the  sides  of  the  cone.  Ether  vapor  is  heavy  and 
falls,  hence  the  towel  prevents  waste  and  facilitates  use. 
Do  not  ''force  the  ether,"  i.  e.,  let  the  animal  have  plenty  of 
air  to  breathe.  Remember  that  etherization  is  not  asphyxia- 
tion. The  man  giving  the  ether  must  think  of  nothing  else. 
If  the  animal  dies  through  his  fault,  he  must  pay  for  an- 


158  EXPURIMF.NT  XXVIII. 

Other,  ( 50  cer.ts).  Watch  especially  the  respiration,  and  when 
in  doubt,  pinch  toot,  to  see  if  leg  reflex  is  present ;  also  note 
the  corneal  reflex,  which  consists  in  a  closing  of  the  lid 
when  the  cornea  is  lightly  touched.  When  well  under,  the 
animal  should  breathe  regularly  and  quietly.  If  the  respir- 
ation becomes  irregular,  with  pauses,  and  the  reflexes  are 
present,  the  animal  is  "coining  out"  and  needs  more  ether. 
If  the  respiration  stops,  or  becomes  convulsive,  immediately 
test  the  reflexes,  and  if  the  reflexes  are  absent  stop  the 
ether;  start  artificial  respiration,  by  rhythmically  compress- 
ing the  chest  laterally ;  and  call  instructor.  The  amount 
of  ether  should  be  lessened  when  the  third  stage 
is  reached,  and  only  a  little  given  at  intervals,  to  keep  the 
animal  asleep.  In  case  coarse  rales  caused  by  collection  of 
mucus  are  heard,  swab  out  the  throat  with  absorbent  cotton 
on  large  forceps. 

DIRECTIONS    TO   OPERATOR. 

When  the  animal  is  sufficiently  under  to  have  stopped 
struggling,  fasten  it  on  animal-board,  by  placing  a  noose 
about  each  leg  above  the  hock,  and  tying  the  cords  to  the 
cleats  on  the  sides  of  the  animal-board.  Put  head  in  head- 
holder.    The  instructor  will  show  the  method  of  application. 

As  soon  as  the  animal's   head  has  been  placed  in  the 
head-holder,  remove  the  hair  from  front  of  throat  for  a 
space  an  inch  wide,  and  from  top  of  thyroid  cartilage  to« 
sternum.    Put  the  hair  in  a  battery  jar. 

.  A  rolled  towel  placed  beneath  the  neck  may  help  oper- 
ator by  putting  parts  under  tension.  Sponge  ofif  the  loose 
hairs,  and  as  soon  as  the  reflexes  have  ceased,  make  a 
median  incision  with  scalpel  through  skin,  from  top  of 
thyroid  cartilage  to  near  top  of  sternum.  Avoid  veins  at 
lower  part  of  incision.  Cut  through  the  platysma  muscle 
in  the  median  line.    Tie  off  any  large  vessels  that  have  been 


CIRCULATION  AND  RESPIRATION  OF   MAMMAI.. 


159 


cut,  and  have  assistant  sponge  off  blood  with  warm  salt 
solution.  Separate  sterno-mastoid  from  sterno-hyoid ;  this 
brings  the  sheath  of  carotid  artery  into  view.  Close  to  the 
artery  are  the  veins  and  nerves.  From  this  time  on  it  will 
probably  be  better  to  tear  away  the  fascia  longitudinally 
Avith   the   blunt   end   of    a   director   or   similar   instrument, 


..--'     M.    stylohyoideus    major. 
••     N.   hypoglossal. 
"     Superior    laryngeal. 
Descendens  noni. 
2  roots  of  depressor  nerve. 

Vagus. 

Depressor. 

Sympathetic. 

Carotid    artery. 

Trachea. 

M.    sterno-mastoid. 


Fig.  32.     Dissection  of  nerves  of  left  side  of  neck  of  rabbit.     The  trachea  has 
been  pulled  to  the  right  and  the  nerves  to  the  left. 


rather  than  use  a  knife.  The  descendens  noni  lies  super- 
ficially ;  the  vagus  lies  behind  the  carotid ;  to  the  inside  of 
the  vagus  are  the  sympathetic  and  depressor  nerves.  Isolate 
the  vagus,  the  largest  of  these,  for  a  distance  of  an  inch  or 
more  and  pass  a  thread  under  it,  tying  the  ends  together  so 
that  the  nerve  can  be  lifted  by  the  loop.  Avoid  pinching, 
stretching,  or  otherwise  injuring  the  nerve. 


l6o  e:XPKRIMKNT  XXVIII. 

Prepare  the  upper  part  of  carotid  for  insertion  of  can- 
nula, by  carefully  separating  it  from  its  sheath  for  a  dis- 
tance of  at  least  an  inch.  Pass 
c//  two  ligatures  under  it,  and  tie 

^      //      /N3  one    of    them    tightly    at    the 

V:^  f    I'y^^x  upper  end  of  the  exposed  part 

— ^j  — i>"^^\; — ^        of  the  artery  ;  place  the  other 
"^  /,      ^  so  that  it  can  be  used  at  short 


Fig.  33.    Method  of  inserting  can-        HOticC     tO     tie    the     Caunula     in 

tlT^S^^-ot^^^      place.     Apply  a  pair  of  bull- 

where  the  cannula  IS  to  be  inserted ;  dog    forCCpS    tO    loWCr   part    of 

B,   cannula ;   C,   forceps ;    D,   loop   of  ,            ,         i      ,       /v  i  i         i    atvi 

ligature  placed  around  artery,  to  the  artcn,^  tO  Shut  Off  blOOd.    ihere 

proximal    side   of   point   where   can-  /          mptKnrIc    nf   inQPr+ino- 

nula   is   to   be   inserted;    E,   bull-dog  ^^^   ^^^  *-l    mCinoaS    01    inserting 

^°'''=^P^-  a  cannula,  viz:  i.    Grasp  with 

fine  pointed  forceps  as  sina.ll  a  part  of  the  arterial  Avail  as 
3'ou  can  hold  securely,  and  with  fine  pointed  scissors  make 
a  diagonal  slit  in  the  direction  of  the  heart  and  through 
about  half  the  width  of  the  artery.  Still  holding  the  .flap, 
insert  the  cannula  supplied  by  the  Instructor,  and  let  the  as- 
sistant tie  it  in  firmly  with  the  ligature  which  has  been  placed 
there  for  the  purpose.  2.  Place  the  index  finger  of  the 
left  hand  beneath  the  artery ;  with  sharp,  fine  pointed  scis- 
sors make  a  cut  in  the  wall  of  the  artery ;  and  without  with- 
drawing the  finger  insert  the  cannula.  It  is  of  advantage  to 
put  the  cannula  into  the  upper  part  of  the  artery,  so  that  the 
lower  part  can  be  used  in  case  the  cannula  has  to  be  put  in  a 
second  time. 

Fill  cannula  with  anticoagulation  fluid,  by  means  of  a 
fine  pipette,  the  instant  the  cannula  is  tied  in.  Now  without 
losing  time  place  the  animal-board  so  that  the  cannula  can 
be  readily  connected  with  the  bulb  on  the  manometer  outfit. 
Make  sure  that  the  cannula,  bulb  and  connecting  tube,  are 
full  of  anti-coagulation  fluid,  and  then  connect  them.  Fasten 
the  tube  of  the  bulb  in  a  burette  clamp,  in  the  position  which 
will  bring  the  least  possible  strain  on  the  artery.  Apply  the 
pneumograph  and  connect  with  tambour. 

a.     Measure  of  the  Blood  Pressure  in  the  Carotid. 

As  soon  as  the  cannula  has  been  fastened  to  bulb,  remove 
bull-dog  forceps,  and  make  sure  that  there  is  no  leak  be- 


CIRCULATION  AND  RESPIRATION  01'    MAMMAL.  l6l 

tween  the  cannula  and  the  artery.  The  blood  should  be 
seen  to  enter  the  cannula  and  diffuse  into  the  fluid,  in  the 
bulb.  Tf  all  is  right,  gradually  open  stop-cock  i.  The 
manometer  float  should  rise,  and  the  height  of  arterial  pres- 
sure be  recorded.  Start  the  drum  and  take  four  records, 
stopping  the  drum  and  marking  the  position  of  the  writing 
points  between  them.  Notice  that  curve  shows  larger  waves 
of  pressure  due  to  respiration,  and  upon  these,  smaller 
waves  caused  by  heart  beats.  The  small  waves  do  not  show 
the  amount  of  blood  expelled  by  heart,  but  the  effect  of  cor- 
responding pressure  changes  in  the  artery,  on  the  mercury  in 
the  manometer. 

b.  B.rcitation  of  the  Peripheral  End  of  the  Right  Vagus. 

The  operator  now  ties  two  ligatures  around  the  vagus 
near  each  other  and  close  to  the  center  of  the  isolated  por- 
tion of  the  nerve,  and  then  cuts  the  nerve  between  them. 
Remember  to  mark  position  of  writing  points  before  each 
test.  Place  peripheral  end  of  vagus  on  the  electrodes,  taking 
care  that  they  touch  nothing  else.  Closekey  of  primary  cir- 
cuit ;  see  that  vibrator  works  well.  Record  a  curve  of  normal 
pressure  for  15  seconds  and  then  let  the  apparatus  man 
open  short-circuit  key.  If  weak,  the  current  should  slow 
the  heart,  and  if  strong,  should  stop  it.  Strengthen  current 
if  necessar}'.  Excite  for  only  10  seconds,  then  close  short 
circuit  and  watch  recovery  15  seconds.  Repeat  the  experi- 
ment 4  times,  to  provide  a  record  for  each  student,  and  give 
an  interval  of  half  a  minute  between  the  succeeding  tests. 

c.  Excitation  of  Central  End  of  the  Vagus. 

Now  while  taking  record  of  blood  pressure  and  respir- 
ation, excite  central  end  of  vagus  with  weak  current.  Affer- 
ent fibers  are  excited,  (sensory  of  the  air  passages  and 
"respiratory  pressor  and  depressor"  of  the  lung),  resulting 
in  the  following  :— 

I. — Excitation  of  respiratory  center,  causing  change  in 
amount  and  frequency  of  respiration. 

2. — Excitation  of  vaso-motor  center,  tending  to  produce 
a  rise,  but  occassionally  a  fall  of  blood  pressure. 


J  62  e;xpkrimi-nt  xxvin. 

3. — Excitation  of  vagus  center,  which  frequently  slows 
the  heart  through  a  crossed  reflex,  and  causes  a  fall  of  pres- 
sure in  spite  of  vaso-constriction  which  may  occur. 

4. — If  current  is  too  strong,  and  the  anesthesia  incom- 
plete, there  may  be  reflex  excitation  of  motor  centers,  caus- 
ing convulsive  movements  which  may  mask  the  other  effects 
and  cause  a  rise  of  blood  pressure. 

Now  let  the  operator  tie  off  the  right  carotid  below  can- 
nula, and  remove  canula  from  artery.  L,et  assistant  hold  a 
dish  under  the  cannula  and  then  disconnect  bulb  from 
manometer  tube ;  wash  bulb  and  cannula  out  thoroughly ; 
connect  bulb  again  with  manometer  tube ;  return  cannula  to 
the  instructor.  ITandle  bulb  and  cannula  with  care,  as  they 
are  fragile  and  hard  to  replace.  Sponge  up  all  fluid  spilled 
and  put  apparatus  in  order  for  next  experiment.  Discon- 
nect and  remove  pneumograph. 

d.  Excitation  of  Peripheral  End  of  Left  Vagus. 

The  student  who  is  to  operate,  takes  the  animal-board 
to  the  operating  table  and  proceeds  to  prepare  the  artery 
and  nerve  of  the  left  side,  the  other  students  doing  the  work 
assigned  in  the  schedule.  When  the  operation  is  finished, 
test  and  record  blood  pressure,  when  the  left  vagus  is 
excited. 

e.  Excitation  of  Sciatic  Nerve. 

The  sciatic  nerve  lies  beneath  the  vastus  externus  on  the 
middle  of  the  external  surface  of  the  thigh.  Remove  hair 
over  region ;  cut  skin  longitudinally  for  2  inches ;  cut 
through  vastus  externus  and  expose  the  nerve.  Animal 
must  he  ivell  under  the  ether  before  the  nerve  is  handled,  and 
especially  on  stimulating.  Pass  a  ligature  under  nerve  and 
tie  ends  together.  When  ready  to  excite,  ligate  peripheral 
end  of  part  exposed  and  cut  peripherally  to  ligature;  place 
nerve  across  electrodes,  which  must  not  touch  anything  else, 
then  apply  current.  See  rise  of  blood  pressure  due  to  re- 
ilex  vaso-constriction,  or,  as  not  infrequently  occurs,  a  fall 
due  to  reflex  vaso-dilation.  If  current  is  too  strong  or  ani- 
mal not  well  under,  convulsive  movements  will  be  produced 
which  will  mask  the  effect  desired. 


CIRCULA'i'ION  AND  RESPmATlON  OF   MAMMAL.  1 63 

/.     Blood  Pressure  during  Asphyxia. 

Expose  the  trachea  and  place  loiv  dozLu  upon  it  a  clamp 
used  for  rubber  tubing,  so  that  the  trachea  can  be  closed 
off  quickly.  Start  drum  at  rate  of  one  or  two  mm.  per 
second,  then  clamp  off  trachea,  marking  the  instant  this  is 
done  by  means  of  short  circuit  key.  Observe  the  following 
stages : 

I.- — Dyspnea.  Blood  pressure  rises  gradually.  Deep- 
and  prolonged  respirations,  with  short  expirations,  soon. 
affect  the  blood  pressure  in  a  marked  manner. 

2. — Convulsions.  Each  convulsion  is  accompanied  by 
a  rise  of  blood  pressure. 

3. — AVeakening  and  slowing  of  heart  beats :  respirations 
feebler  and  fewer ;  finally  both  heart  beats  and  respirations 
stop. 

g.     Elasticity  of  Lung  Tissue. 

Make  incision  .in  trachea;  insert  cannula:  and  connect 
with  a  water  manometer,  noting  the  level  of  the  fluid.  Open 
the  chest  and  note  the  new  level  to  which  the  water  in  the 
tube  rises  when  air  enters  the  chest  and  the  lungs  collapse. 
The  air  which  leaves  the  lung  when  the  chest  is  opened  is 
the  "residual"  air.  (see  diagram,  ICxperiment  XLI).  To 
open  chest,  first  make  an  incision  with  the  knife  over  the 
entire  length  of  the  sternum :  grasp  ensiform  cartilage  with 
strong  forceps  ;  push  point  of  strong  shears  through  chest 
wall  at  end  of  ensiform  cartilage  and  cut  sternum  length- 
wise, in  the  median  line,  to  within  2  cm.  of  its  upper  end. 
Keep  point  of  shears  close  to  sternum,  to  avoid  cutting  lungs 
or  other  organs.  Pull  the  cut  edges  of  the  sternum  apart 
and  see  the  collapsed  lungs.  Remove  the  lungs ;  put  them 
in  water,  and  notice  that  they  float.  This  is  because  of  the- 
''mimimal  air"  which  is  imprisoned  by  the  collapsed  bronchi. 
The  fact  that  the  lungs  float,  provided  that  there  are  no 
gases  due  to  decomposition,  is  considered  a  proof  that  the 
animal  has  breathed. 


164  expi3rime;nt  XXVIII. 

NOTES. 

In  mounting  the  curves,  be  careful  to  preserve  the  part 
of  each  record  which  shows  the  relation  of  writing  points, 
and  the  portion  showing  15  seconds  before,  and  15  seconds 
after  the  period  of  stimulation.  Draw  three  pairs  of  long 
vertical  lines  from  the  time  curve  through  the  pressure  and 
respiration  curves,  so  as  to  enclose  periods  of  6  seconds  be- 
fore, during,  and  just  after  cessation  of  stimulation. 

To  find  the  blood  pressure,  measure  from  the  base  line, 
.given  by  the  time  signal,  to  the  blood  pressure  curve,  using 
the  middle  of  the  pulse  beats  for  the  mean  pressure,  and 
multiply  by  two.  For  heart  rate,  count  the  pulse  beats  in 
the  6  seconds  between  the  verticals  and  multiply  by  10.  In 
a  similar  manner  determine  the  number  of  respirations  per 
minute.  Write  the  figures  obtained,  on  the  cardboard  above 
the  mounted  curve,  at  points  corresponding  to  the  obser- 
vations. 

Give  brief  statements  of  the  results  obtained  under  each 
of  the  subheadings  of  the  experiment,  stating  the  cause  of 
the  changes  in  arterial  pressure,  pulse,  and  respiration  pro- 
duced bv  the  excitations. 


CIRCULATION  AND  RKSPIRATION   OF   MAMMAL.  165 


l6.6  EXPERIMENT  xxviri. 


CIRCULA1I0X   AND  RESPIRATION   OP    MAMMAL.  167 

EXPERIMENT  XXIX 
Circulation  and  Respiration  of  the  Mammal,  Continued. 

a.     Excitation  of  Right  Depressor  Nerve. 

The  depressor  is  an  afferent  nerve  from  the  root  of  the 
aorta,  and  hence  excitation  of  the  peripheral  end  has  no 
effect.  Excitation  of  central  end  has  little  effect  on  the 
cardiac  centers,  but  causes  dilation  of  peripheral  vessels  by 
inhibition  of  the  vaso-constrictor  center. 

Expose  the  carotid  as  in  Experiment  XXVIII.  To  find 
the  depressor,  remember  that  vagus  lies  behind  the  artery 
and  the  depressor  and  the  sympathetic  to  the  inner  side.  High 
up  the  vagtis  gives  off  a  transverse  branch,  the  superior 
laryngeal,  (see  diagram,  Experiment  XXVIII)  to  the 
larynx.  The  depressor  arises  as  a  very  slender  nerve  by  two 
branches  from  this,  or  one  from  this  and  one  from  the 
vagus.  Find  the  place  of  division,  then  trace  the  nerve  down 
for  2  cm.  or  more,  tie  a  thread  about  it  and  cut  peripherally 
to  thread.  Handle  nerve  with  utmost  care  and  see  that  it 
does  not  drv^ 

Now  isolate  carotid  and  insert  cannula;  connect  with 
manometer ;  apply  pneumograph ;  record  normal  curves  of 
blood  pressure  and  respiration.  Excite  central  end  of  de- 
pressor while  drum  is  running.  Excite  only  long  enough  to 
produce  an  evident  effect,  and  let  drum  run  till  recovery  is 
well  under  way.  Take  four  records,  waiting  in  each  case 
until  recovery  is  complete.     Is  the  rate  of  heart  changed? 

b.  Excitation  of  Left  Depressor  Nerve. 

Prepare  depressor  and  carotid  of  other  side  and  repeat 
above  experiment. 

c.  Tracheotomy  and  Artificial  Respiration. 

Remove  cork  of  bottle  in  outfit  for  artificial  respiration, 
put  about  2  cm.  of  ether  in  the  bottom,  and  replace  the  cork. 
Make  an  incision  in  the  trachea,  insert  the  cannula,  and  tie 


;i68  EXPICRIMENT    XXIX. 

it  firmdy  in  place  with  a  strong-  ligature.  Now  give  the 
ether  by  holding  the  cone  above  the  tracheal  cannula. 
While  this  is  being  done,  the  apparatus  man  should  pre- 
pare artificial  respiration  apparatus  and  test  the  amount  of 
ether  it  gives.  Regulate  supply  of  ether  by  means  of  clamps 
on  tubes  connecting  with  ether  bottle. 

To  open  the  chest,  first  make  an  incision  with  knife  over 
entire  length  of  sternum,  grasp  ensiform  cartilage  with 
strong  forceps ;  push  point  of  shears  through  chest  wall  at 
end  of  cartilage  and  cut  sternum  lengthwise,  in  the  median 
line  to  within .  2  cm.  of  its  upper  end.  Keep  point  of 
shears  close  to  sternum  to  avoid  cutting  lungs  or  other  or- 
gans. Special  care  is  necessary  at  the  upper  part,  or  blood 
vessels  will  be  cut. 

As  soon  as  the  chest  is  opened,  with  clamp  on  side  tube 
open,  connect  tracheal  cannula  with  ether  bottle,  and  start 
bellows,  pumping  at  rate  of  once  a  second.  Screw  up  clamp 
on  side  tube  until  the  lungs  are  seen  to  expand  and  relax 
well. 

Observe  the  effect  of  artificial  respiration  on  the  curve 
of  blood  pressure.  The  respiratory  waves  of  the  curve  are 
now  reversed,  the  curve  falling  soon  after  the  air  begins  to 
enter  the  lungs,  and  rising  soon  after  beginning  of  expir- 
ation, due  to  elastic  recoil  of  lung.  Does  your  curve  cor- 
roborate this  statement?    If  not,  why? 

d.  The  Current  of  Action  of  the  Heart. 

Draw  chest  walls  apart  with  the  hooks  provided.  Open 
the  pericardium  widely,  faking  care  not  to  cut  the  heart  in 
doing  so.  Now  hold  the  bone  of  a  nerve-leg  preparation  in 
forceps,  with  nerve  hanging  down ;  let  the  nerve  lie  upon  the 
beating  ventricle  lengthwise;  the  muscle  should  contract 
with  each  beat.    If  it  does  not,  lift  it  and  try  again. 

e.  Observation  of  Bxposed  Heart  during  Vagus  B.vcitar- 

tion. 

Observe  the  effect  of  excitation  of  the  peripheral  end  of 
a  vagus  nerve  on  the  rate  and  strength  of  beat  of  the  ex- 
posed heart.    Test  with  weak,  medium,  and  strong  currents. 


CIRCUr.ATION  AND  RESPIRATION   OF    MAMMAI,.  1 69 

/.     Tension  of  Ventricle  during  Systole  and  Diastole. 

Take  the  ventricle  gently  between  the  thumb  and  fingers, 
and  feel  it  harden  with  each  systole. 

g.     Observation   of   the   Changes  in  Heart   during  Death 
from  Asphyxia. 

Open  chest  widely  so  as  to  obtain  a  good  view.  Stop 
artificial  respiration  and  observe  the  effects  of  asphyxia  on 
the  rhythm  of  auricles  and  ventricles  as  the  heart  dies.  Make 
notes  of  the  order  in  which  the  strength  of  beat  of  auricles 
and  ventricles  changes.  Notice  any  irregularities,  and 
w^hich  auricle  or  ventricle  gives  out  first.  What  part  of 
heart  is  most  distended  at  death? 

h.     Innervation  of  Diaphragm  by  the  Phrenic  Nerves. 

These  nerves  are  easily  found,  running  down  lateral 
and  posterior  sides  of  pericardium.  Excite  one,  then  the 
other,  observing  contraction  of  diaphragm  from  upper  side. 
Open  the  abdominal  cavity  by  one  incision  in  median  line; 
observe  relations  of  organs;  push  viscera  down  and  excite 
phrenic  while  looking  at  under  side  of  diaphragm.  Notice 
that  contraction  of  diaphragm  depresses  the  floor  of  the 
chest ;  thus  increasing  chest  cavity  and  lessening  abdominal 
cavity. 

i.     Peristalsis  of  Intestines. 

Observe  any  peristaltic  movements  that  may  occur  be- 
cause of  exposure  to  air  and  loss  of  blood.  See  direction 
of  waves.  Watch  for  anti-peristalsis.  Try  effect  of  mechan- 
ical and  electrical  stimulation  of  stomach  and  intestines. 
Excite  bladder  electrically. 


NOTES. 

Write  up  the  notes  as  directed  in  the  preceding  experi- 
ment. 


lyo 


i!;xpr;RiMEN'r  xxix. 


CIRCUIvATlON  AND  RESPIRATION  OF   MAMMAL.  171 


1^2  r;xrr;RikE:N'r  xxix. 


CAROTID   rULSlJ  IN    MAN. 


173 


EXPERIMENT  XXX. 

The  Carotid  Pulse  in  Man. 

The  Form  of  the  Pulse  Wave,  and  Bifect  of  Arterial  Pres- 
sure. 

The  pulse  is  a  wave  of  pressure  which  is  transmitted 
along-  the  arterial  system  when  the  heart  drives  blood  into 
the  aorta.  Each  systole  raises  the  pressure  suddenly,  giving 
what  is  called  the  systolic  pressure,  and  during  the  follow- 
ing diastole  the  pressure  falls,  until,  just  before  the  next 
systole,  the  diastolic  pressure  is  reached.  The  amount  that 
the  pressure  changes,  that  is  the  difference  between  the 
systolic  and  diastolic  pressures  is  known  as  the  pulse  pres- 
sure, while  the  pressure  midway  between  the  systolic  and 
diastolic  is  for  ordinary  purposes  spoken  of  as  the  mean 
pressure,  although  on  account  of  the  distribution  of  the  pres- 
sure values  from  systole  to  systole,  it  is  not  the  true  mean. 


A     B 


Fig.  34.  Sphygmograms  of  two  pulse  beats, 
one  taken  when  the  pressure  was  quite  high 
and  the  other  when  it  was  quite  low.  A, 
crest  of  primary  wave ;  B,  dicrotic  notch ;  C, 
dicrotic    wave. 


Under  ordinary  conditions  the  caliber  of  an  artery  can- 
not be  seen  to  change  when  the  pulse  wave  travels  through 
it ;  nevertheless,  if  the  vessel  be  slightly  compressed  by  the 
finger,  the  pressure  change  can  be  felt,  and  if  the  finger 
has  been  trained,  not  only  the  extent  but  character  of  the 
pulse  wave,  and  the  amount  of  the  systolic  and  the  diastolic 
pressure  can  be  more  or  less  accurately  estimated.     If  a 


174       .  EXPERIMENT  XXX. 

suitable  instrument,  a  sphymograph,  be  applied  to  the  skin 
over  the  artery  a  record  of  the  pulse  pressure  changes  may 
be  obtained.  The  instrument  will  not  measure  the  pressure, 
and  the  record  fails  to  give  an  absolutely  correct  picture  of 
the  course  of  the  pressure  oscillations,  because  they  are 
modified  by  the  intervening  tissues  and  by  the  incapacity 
of  an  instrument  to  follow  with  exactness  all  the  rapidly 
alternating  phases  of  the  pressure  changes.  Nevertheless, 
the  most  marked  changes  in  the  pressure  are  well  pictured 
both  with  respect  to  time  and  extent,  and  the  records  give 
information  which  in  certain  conditions  are  not  only  of 
scientific  interest  but  of  decided  clinical  value. 

The  form  of  the  pulse  curves  varies  greatly  with  the  in- 
strument used  and  the  artery  from  which  the  pulse  is  re- 
corded.    A  typical  pulse  curve  is  usually  described  as  con- 
sisting of  a  rapid  primary  up-stroke,  the  anacrotic  limb,  and 
a  prolonged  fall,  the  catacrotic  limb,  on  which  a  number  of 
oscillations  are  to  be  seen,  (see  Fig.  34).    One  of  these  oscil- 
lations, which  shows  one-third  the  way  along  the  curve,  is 
always  to  be  seen.    It  consists  of  a  more  or  less  deep  notch, 
the  dicrotic  notch,  and  is  followed  by  a  definite  wave,  the 
dicrotic  wave.    The  dicrotic  notch  is  of  especial  importance 
because  the  descending  limb  of  the  notch  marks  the  closure 
of  the  aortic  valve.    The  notch  therefore  divides  the  curve 
into  a  systolic  portion,  during  which  the  left  ventricle  is  in 
communication  with  the  aorta,  and  a  diastolic  portion,  dur- 
ing which  the  arteries  are  shvit  off  from  the  heart.     The 
systolic  portion  gives  indication,  therefore,  of  the  way  the 
ventricle  imparts  pressure  to  the  blood  in  the  artery  and  the 
resistance  which  it  encounters,  and  the  diastolic,  of  the  con- 
ditions in  the  arteries,  themselves,  which  determine  the  rate 
of  fall  and  oscillations  of  the  pressure.    Occasionally  a  wave 
or  shoulder  is  observed  on  the  ascending  limb,  an  anacrotic 
wave,  which  usually  implies  that  there  is  some  unusual  re- 
sistance offered  to  the  flow  of  the  blood  from  the  ventricle. 
Almost  always  a  wave  is  to  be  seen  on  the  descending  limb 
preceeding   the   dicrotic  notch,    and    called   the   predicrotic 


CAROTID   PULSP;  IN    MAN.  1 75 

wave.  This  in  many  cases  at  least  is  an  instrumental  error, 
due  to  the  fact  that  the  recording-  lever  has  been  thrown 
too  far,  and  has  made  a  depression  on  the  curve  when  it 
recoiled.  Waves  may  also  be  seen  following-  the  dicrotic 
notch,  post  dicrotic  waves,  which  are  generally  supposed  to 
be  reflected  waves  from  various  points  along  the  walls  of 
the  arteries.  Not  infrequently  there  is  a  slight  wave  to  be 
seen  just  at  the  close  of  the  diastolic  period ;  this  wave, 
coming  at  the  time  that  the  auricle  is  completing  the  filling- 
of  the  ventricle,  suggests  that  the  sudden  swelling  of  the 
ventricle  may  have  imparted  a  slight  push  to  the  root  of 
the  aorta. 

The  dicrotic  notch  is  of  additional  importance,  because 

the  height  of  the  notch  above  the  base- 

p-~S^  line  gives  an  indication  of  the  rate  of  fall 

"  -'- -^^^        of  diastolic  pressure.    When  the  pressure 

is  maintained  during  diastole,  the  post- 

V       c  dicrotic  portion   of  the  tracing   falls   in 

\\/'"i       I  nearly   a   straight   line   and   the   dicrotic 

L  i-A-V-^^S^^J-         notch  is  high  ;  when  the  pressure  falls  off 

rapidly  during  diastole,  the  post-dicrotic 

Fig.     35.       Diagram  ^-  r    11       •  u"    u     •  1 

of  a  high  pressure  portion  lalls  m  a  curvc  which  IS  mark- 
foV^  pressurT  p°uisl  cdly  couvcx  toward  the  abscissa,  and,  es- 
iotch;  \  dicrouc  pecially  if  the  mean  pressure  is  low,  the 
wave.  dicrotic  notch  is  deep. 

In  Fig.  35  the  unbroken  lines  give  the  "skeleton"  oi  the 
pulse,  that  is,  show  the  general  course  of  the  wave  of  pres- 
sure, and  the  broken  lines  indicate  how  secondary  waves 
may  be  superposed  on  this.  When  the  pressure  is  high,  the 
waves  are  generally  few  and  small,  and  when  it  is  low,  they 
are  often  many  and  large. 

Apparatus. — Mount  a  recording  tambour  on  a  stand  and 
connect  it  with  an  open  tambour  designed  for  carotid  artery, 
leaving  side  tube  open.  See  that  the  lever  of  the  tambour  is 
horizontal.  Apply  the  open  tambour  to  the  skin  of  the  neck 
over  the  artery,  and  fasten  it  in  place  with  the  U-shaped 
spring,  placing  the  ball  of  the  spring  in  the  socket  on  the 


176  EXPKRIMBINT   XXX. 

back  of  the  tambour  and  placing  the  block  against  the 
opposite  side  of  the  neck.  Then  test 
the  working  of  the  outfit  by  pinching 
the  side  tube.  With  each  heart  beat 
there  should  be  an  excursion  of  the 
lever  of  at  least  5  mm.  Adjust  posi- 
tion of  tambour  on  neck,  and  pressure 
of  spring  to  give  the  largest  pulsation, 
Fig.  36.    Tambour  and      ^"h^n  bring  Writing  point  very  lightly 

neck  spring  used  to  study      agaiust  drum.     Start  drum  at  5  mm. 

the  human   carotid  pulse.  ,  ,  .  ,        ,  ,  .   , 

A,   spring;   B,   baii-and-      per    sccoud,    close    Side    branch    with 

socket   joint,    on   back    of  •  ^•  j  j  j.l_  r  it, 

open  tambour;  c,  block,  spmig  clip  and  rccord  the  curve  of  the 
pulse.  Unless  the  friction  of  writing 
point  upon  drum  is  made  as  slight  as  possible,  small  waves 
of  the  pulse  curve  will  be  obscured.  Mark  on  the  curves  to 
indicate  the  primary  wave  and  the  dicrotic  notch.  Usually 
the  lever  is  thrown  too  high,  and  as  it  falls  depresses  the 
rubber  membrane  and  records  a  notch  which  might  be 
mistaken  for  the  dicrotic  notch.  The  second  notch  is  gen- 
erally the  dicrotic,  and  is  followed  by  a  wave  larger  than 
that  which  would  be  given  by  the  recoil  of  the  membrane. 
This  is  the  dicrotic  wave.  Do  pre-dicrotic  or  post-dicrotic 
waves  occur  in  the  record?  Take  records  with  four  widely 
different  speeds  of  drum,  and  observe  the  effect  on  the  form 
of  the  curve. 

a.  The  Pulse  Rate. 

Mount  a  time  signal  to  write  below  the  pulse  curve,  con- 
nect it  with  the  clock  circuit,  start  drum  at  5  mm.  per  sec- 
ond, and  record  the  curves  of  time  and  pulse.  Draw  per- 
pendiculars at  intervals  of  ten  seconds  cutting  the  pulse 
curve,  and  determine  the  rate  of  the  pulse  per  minute. 

b.  Duration  of  Systole  and  Diastole. 

Mount  a  fork  in  place  of  the  time  signal ;  see  that  lever 
is  horizontal  z^'heii  the  side  tube  is  open;  and  record 
curves  of  pulse  and  fork  with  the  fastest  speed  of  drum 
given  by  clockwork.  Then,  without  moving  drum,  remove 
clip  from  side  tube,  and  record  a  base  line   for  the  pulse 


CAROTID  PULSE  IN    MAN.  177 

curve.  When  the  curves  have  been  fixed,  draw  arcs  with 
dividers  from  beginning  of  primary  wave  and  from  bottom 
of  dicrotic  notch  to  the  base  Hne,  using  a  radius  equal  to 
the  length  of  the  writing  lever  and  centers  on  the  base  line. 
Draw  perpendiculars  from  the  points  where  the  arcs  cut 
the  base  line,  through  the  fork  curvx.  If  one  triangle  is 
placed  horizontally  beneath  the  fork  curve  and  held  firmly 
in  place,  the  other  can  be  slid  along  it,  and  the  verticals  be 
drawn  rapidly  and  exactly.  Count  up  the  fork  waves  be- 
tween the  perpendiculars,  and  thus  determine  the  duration 
of  systole  and  diastole.  In  counting  the  vibrations  of  the 
fork,  it  is  best  to  make  a  little  mark  over  every  fifth  vibra- 
tion. This  can  be  done  rapidly  if  one  learns  to  see  four 
vibrations  at  a  glance  and  marks  the  fifth.  Make  this  deter- 
mination for  five  consecutive  pulse  beats  and  state  the  aver- 
age in  your  notes. 

c.     Effect  of  Exercise. 

Go  through  the  form  of  taking  a  normal  record^  as  in^  A-" 
to  make  sure  that  the  neck  tambour  is  properly  adjusted, 
and  that  the  recording  tambour  is  writing  well.  Then, 
without  moving  the  drum  or  either  tambour,  detach  the 
rubber  tube  where  it  joins  the  glass  T.  Take  a  quick  run 
down  stairs  and  back,  connect  up  the  tambour  as  soon  as 
possible,  and  record  the  accelerated  pulse.  Determine  dur- 
ation of  systole  and  diastole,  and  calculate  the  heart  rate. 

Which  changes  more  in  the  quickening  of  the  pulse  due 
to  work,  the  systolic  or  the  diastolic  portion  ?  Are  any  other 
changes  in  the  pulse  curve  to  be  observed?  If  so,  describe 
them. 


lyS  EXPERIMENT  XXX. 


CAROTID  VVlSn  JN   MAN. 


179 


l8o  ■  EXPERIMENT   XXX. 


FORM  AND  POSTPONEMIiNT  OF  RADIAL  TULSli. 


EXPERIMENT  XXXI. 


The    Radial    Pulse    Studied   by    the    Tambour    Method. 


Fig.  37.  Method  of  applying  tam- 
"bour  to  wrist,  to  obtain  sphygmo- 
gram  from  the  radial  artery.  A, 
cross  section  of  wrist;  B,  back 
toard  of  arm  support ;  C,  cabinet 
maker's  clamp ;  D,  clamp  fastening 
L  rod  to  the  horizontal  rod  of  arm 
rest ;  E,  clamp  fastening  tube  of 
tambour  to  short  arm  of  L,  rod ; 
F,  tambour  with  disk,  and  prop  to 
rest    on    artery. 


Connect  a  recording  tambour  with  a  tambour  designed 
for  radial  artery,  leaving  side  branch  of  tube  open.    Arrange 

arm  rest  and  tambour  as 
shown  in  the  diagram.  Mark 
the  point  on  left  wrist  where 
strongest  pulse  is  felt.  Sub- 
ject seats  himself  comfortably 
in  chair,  holding  one  end  of 
arm  rest  in  lap,  while  other 
end  is  placed  on  table  or  stool 
so  as  to  tilt  it  at  a  suitable 
angle  for  the  arm  to  rest  eas- 
ily. Place  arm  on  rest  with 
marked  point  toward  tam- 
bour; fasten  thumb  with  loop 
of  cloth,  using  holes  in  back 
board;  apply  button  of  tambour  to  marked  spot,  and  adjust 
tambour  so  that  rod  bearing  button  is  in  line  with  tube  of 
tambour  and  perpendicular  to  surface  of  wrist.  Vary  the 
pressure  on  artery  by  sliding  tube  of  tambour  in  clamp 
until  largest  pulsation  is  given.  An  excursion  of  3-5  mm. 
with  each  heart  beat  should  be  secured,  but  a  smaller  move- 
ment will  suffice  where  this  cannot  be  obtained.  The  arm 
must  be  relaxed  and  perfectly  quiet. 

a.  Form  of  Radial  Pulse. 

Record  the  radial  pulse  on  a  drum  and  observe  whether 
the  same  waves  appear  as  in  the  carotid  pulse. 

b.  Postponement  of  the  Radial  Pulse. 

Arrange  to  write  carotid  and  radial  pulse  and  fork 
curve  in  same  vertical  line.  Make  sure  that  the  levers  of 
the   tambours   are   horizontal.      Mark   relative   position   of 


1 82  I^XPURTMF,NT    XXXI. 

points,  then  record  the  three  curves  with  fastest  speed  given 
by  kymograph.  Without  disturbing  apparatus,  remove 
clips  from  side  tubes  and,  with  the  levers  horizontal,  record 
base  lines  for  the  two  pulse  curves. 

Fix  the  tracing,  and  then,  with  centers  on  the  base 
lines  and  the  lengths  of  the  levers  as  radii,  draw  arcs  from 
beginnings  of  corresponding  primary  waves  to  their  respec- 
tive base  lines ;  then  correcting  for  positions  of  points,  draw 
perpendiculars  through  fork  curve  and  find  duration  of 
postponement  of  radial  pulse  as  compared  with  carotid 
pulse.    Take  average  of  five  consecutive  beats. 


r'ORM  AND  POSTPONKMENT  OI-  RADTvM,  PULSK.  183 


EXPERIMUNT    XXXI. 


INFLUENCES  AFFECTING  RADIAI,  PULSE. 


185 


EXPERIMENT  XXXII. 

The  Radial  Pulse  as  Recorded  by  the  Jacquet  Sphygmo- 

graph. 

This  is  probably  the  most  useful  instrument  for  exam- 
ination of  the  pulse  that  we  have.  It  is  fragile,  and  must  be 
handled  with  care  and  returned  in  good  condition.  The 
strap  A  is  buckled  about  the  left  wrist,  with  the  end  B 
toward  the  hand.     The  instrument  slips  into  groove  C  of 


Fig.   38.     Scheme  of  Jacquet's   sphygmograph. 

base,  and  thumb-screw  D  is  turned  into  socket  E.  The 
paper,  shown  in  cross  section  at  F ,  runs  between  the  roller 
G  and  two  small  wheels  above  it.  Clock  for  moving  paper 
is  wound  by  means  of  large  thumb-nut  H,  started  and 
stopped  by  lever  at  /,  and  lever  /  gives  a  change  of  speed. 
Clockwork  for  time  marker  L,  is  wound  by  means  of  thumb- 
nut  K,  and  gives  fifths  of  a  second.  M  is  a  clasp  for  hold- 
ing L  up  out  of  harm  when  not  in  use.  Cam  wheel  P,  turned 
by  thumb-nut  Q,  varies  the  tension  of  the  spring,  by  which 
button  A''  is  pressed  on  the  artery.     Movements  of  A^  are 


1 86  EXPERIMTJNT  XXXII. 

transmitted  through  rod  R,  to  lever  S,  turning  on  axis  T, 
thence  to  lever  U,  turning  on  axis  V ,  and  finally  to  marker 
W.  Position  o  f  writing  point  on  the  paper  and  the  pressure 
of  button  on  the  artery,  are  regulated  by  thumb-screw  D. 

To  obtain  the  proper  pressure  on  the  artery  it  is  neces- 
sary, therefore,  to  use  both  thumb-nut  Q  and  thumb- 
screw D. 

CAUl'IONS. 

(i)  Be  careful  not  to  injure  the  time  marker.  Raise 
and  lower  it  with  the  fine  point  of  a  knife  or  pencil.  It 
must  always  be  lifted  into  clasp  before  removing  the  paper. 

(2)  A_void  bending  the  writing  pointer  when  inserting 
the  paper. 

(3)  Do  not  wind  the  clockwork  too  tight. 

(4)  Instrument  must  be  held  level  to  record  time  accu- 
rately. 

a.     Normal  Curves  and  Effect  of  Position  of  Body. 

Place  several  strips  of  paper  around  a  drum,  and  blacken 
as  usual,  cutting  the  strips  loose  as  needed.  Place  end  of  a 
strip  between  roller  and  wheels,  start  clockwork,  and  run  the 
paper  in,  to  the  extent  of  2  cm. 

Having  adjusted  instrument  so  as  to  give  the  largest 
pulsation,  proceed  to  make  records  while  sitting  and  stand- 
ing quietly,  using  slow  speed  of  paper.  In  this  and  all  sub- 
sequent tests,  take  care  not  to  move  arm  or  hand  when  the 
record  is  being  written.  Report  the  rate  per  minute  as 
recorded  for  six  seconds. 

b.  Effect  of  Compressing  Brachial  Artery. 

While  the  tracing  is  being  taken,  compress  the  brachial 
artery  with  hand.  ,         '    1    1    j 

c.  Effect  of  Deglutition. 

Start  the  paper  at  the  slow  speed  record  a  few  beats,  then,, 
while  record  continues,  take  several  swallows  of  water  in 
quick  succession,  marking  on  the  record  the  exact  time  whert 


INFLUENCES  AFFECTING  RADIAL  PULSE.  187 

the  swallowing-  begins  and  ends.  Determine  the  rate  be- 
fore, during,  and  after  swallowing.  The  change  in  rate  is 
explained  as  due  to  alteration  of  vagus  influence.  The  swal- 
lowing center  is  in  the  medulla  oblongata  not  far  from  the 
vagus  inhibitory  center,  and  nervous  impulses  overflowing 
from  the  former  affect  the  latter. 

d.  Effect  of  Inhalation  of  Amyl  Nitrite. 

Take  the  record  on  two  strips  of  paper  pasted  together, 
and  use  the  slow  speed.  Record  normal  pulse  for  20  beats, 
then  begin  to  inhale  amyl  nitrite  that  will  be  supplied  by  the 
instructor.  Associate  should  mark  on  record  the  exact  time 
of  inhalation.  Continue  record  to  end  of  paper.  This  drug 
acts  chiefly,  when  taken  in  small  amounts,  on  the  muscles 
in  the  walls  of  the  small  vessels,  causing  a  dilation.  Fall  of 
blood  pressure  and  increased  dicrotism  of  the  pulse  results. 
The  heart  tends  to  compensate  for  the  fall  of  pressure  by 
increasing  its  rate.  The  change  in  the  level  of  the  writing, 
frequently  seen,  cannot  be  taken  as  evidence  of  the  dimin- 
ished arterial  pressure,  because  it  may  be  due  to  a  move- 
ment of  the  wrist.  The  writing  point  must  be  placed  high 
before  the  inhalation  occurs,  or  it  will  run  off  the  lower  edge 
of  the  paper.  Do  not  repeat.  Mark  on  curve  the  place  where 
the  effect  was  the  greatest,  remembering  that  a  deep  dicrotic 
notch  is  an  indication  of  low  blood  pressure.  State  in  the 
notes  what  change  took  place  in  the  heart  rate. 

e.  Valsalva's  Experiment. 

Record  20  normal  beats,  then  take  a  deep  breath,  and, 
with  mouth  and  nostrils  closed,  make  a  strong  expiratory 
effort  for  eight  or  ten  seconds,  then  breathe  freely.  Mark 
time  of  each  stage  on  record..  Report  effect  on  rate  and 
shape  of  pulse  curve.  The  latter  is  especially  interesting. 
The  expiratory  effort  drives  the  blood  out  of  the  chest  into 
the  arteries,  and  prevents  entrance  of  venous  blood  into  the 
chest  by  compressing  veins  and  right  heart. 


l8»  EXPERIMENT   XXXTI. 

/.     MilUcr's  Bxperiment. 

Record  20  beats,  then  exhale  as  completely  as  possible, 
and  with  mouth  and  nostrils  closed  make  a  strong  inspiratory 
effort  for  five  seconds,  then  breathe  freely.  Mark  on.  record 
and  report  as  before.  The  forced  inspiration  tends  to  keep 
the  heart  and  large  vessels  dilated,  tends  to  prevent  blood 
from  leaving  chest,  and  causes  a  rush  of  blood  into  the  chest 
by  way  of  the  veins. 


INFLUENCES  AEEECTING  RADIAL  PULSE. 


igo  EXPERIMENT  XXXII, 


CAPIlvIvARY  CIRCULATION.  19I 

EXPERIMENT  XXXIII. 
Capillary  Circulation  in  the  Web  of  the  Foot  of  a  Frog. 

Choose  a  frog  having  little  pigment  in  the  skin  of  the 
foot.  Destroy  the  brain  by  a  pithing  needle,  and  plug  the 
skull  cavity  with  a  pointed  match.  Be  sure  to  have  the 
match  ready  to  insert  at  the  instant  the  pithing  needle  is 
withdrawn,  so  that  the  least  possible  blood  shall  be  lost. 
Inject  I  cc.  of  curara  into  the  dorsal  lymph  space.  When 
the  reflexes  have  begun  to  weaken,  wrap  the  frog  in  moist 
cloth,  place  on  special  stage,  face  down,  and  spread  the  web 
over  the  opening,  keeping  in  place  by  ligatures  tied  to  the 
three  longest  toes,  and  fastened  by  binding  posts  on  the 
stage.  Avoid  stretching  web  too  tightly,  and  keep  it  moist, 
not  wet.    Place  stage  on  microscope  stage. 

Examine  first  with  a  low  power.  If  the  blood  is  not  seen 
to  circulate  through  the  smaller  vessels,  the  web  has  prob- 
ably been  stretched  too  tightly,  or  has  been  allowed  to  dry. 
Decide  which  of  the  vessels  are  arteries,  capillaries  and  veins, 
■observing  where  the  blood  flows  from  large  to  small  and 
from  small  to  large  vessels,  where  the  blood  stream  is  most 
rapid  and  where  it  pulsates.  Do  not  let  preconceived  notions 
cause  you  to  think  that  you  see  what  you  do  not  really  see. 
As  far  as  possible  demonstrate  the  following  phenomena 
to  an  instructor: 

I.  Examine  a  small  artery,  and  observe: — 
a     Pulsating  stream. 

b.  Rapid  axial  stream ;  lighter,  peripheral  layer, — the 

"inert   layer." 

c.  Eddies  of  the  stream  at  a  bifurcation. 

II.  Examine  a  small  vein  and  observe : 

a.  Constant  stream  (sometimes  pulsating  if  the  shock 

from  the  pithing  has  not  been  recovered  from,  and 
there  is  vaso-dilation) . 

b.  Slower  current,  and  less  marked  "inert  layer"  than 

in  artery. 


192  EXPERIMENT  XXXIII. 

III.  Examine  capillaries,  and  observe : 

a.  Frequent  anastomoses. 

b.  Condition  and  behavior  of  corpuscles. 

A.  Red  corpuscles  (erythrocytes). 

1.  Shape,  transparency,  color.    . 

2.  The  number  that  can  pass  abreast  in  a  capil- 

lar)^ 

3.  Position    of    long    ajKis    with    respect    to    cur- 

rent. 

4.  Elasticity,    and    change    in    shape   when   com- 

pressed, or  when  turning  a  corner. 

5.  Passage      through      a      capillary      apparently 

smaller  than  cell. 

B.  White  corpuscles  (leucocytes). 

1.  Shape  and  color. 

2.  Peripheral  arrangement. 

IV.  Vaso-motor  Action. 

Expose  sciatic  nerve,  using  the  utmost  care  not  to  injure 
the  Hood  vessels.  Cut  high  up,  and  dividing  branches, 
raise  from  wound  and  lay  on  a  piece  of  moist  filter  paper 
placed  over  the  skin.  (There  is  an  acid  secretion  on  the 
skin  which  will  injure  the  nerve.)  Of  course  the  nerve 
must  be  handled  as  little  as  possible  and  never  be  com- 
pressed. If  the  frog  is  well  under  the  curara,  excite  nerve 
with  induction  current  at  the  same  time  that  a  suitable  part 
of  the  web  is  being  examined  with  a  low  power.  The  vessels 
should  be  seen  to  grow  smaller  and  the  circulation  should  be 
consequently  slowed  or  stopped. 

V.  Diapedesis,  i.  e.,  Migration  through  Wall  of  Capillary. 

(This  is  optional.)  This  is  not  often  seen  to  occur 
under  normal  conditions,  but  the  phenomenon  is  of  frequent 
occurrence  when  an  irritant  causes  local  inflamation.  This 
can  be  best  studied  in  the  mesentery,  a  slight  burn  from  a 
hot  glass  rod  being  a  suitable  irritant. 

Examine  with  low  power  the  effect  upon  the  circulation 
oi  the  part.  Then  choosing  a  capillary  whose  walls  can  be 
seen  distinctly,  watch  carefully  a  leucocyte  resting  against 


CAPILLARY    CTRCULATION.  I93 

the  wall,  and  obsen^e  its  change  of  shape  as  it  passes 
through  the  wall.  Make  drawing  illustrating  the  method 
of  progression.  Red  corpuscles  do  not  pass  through,  unless 
the  walls  have  been  greatly  injured,  since  they  do  not 
possess  amoeboid  power. 

VI.     The  Capillaries  of  the  Human  Skin  Will  Be  Demon- 
strated. 


194 


EXPERIMENT  XXXI II. 


CILIA.  195 


EXPERIMENT  XXXIV. 

Cilia. 

Cilia  play  an  important  role,  by  supplying  the  motor 
power  to  many  forms  of  separate  cells,  and  in  moving  sub- 
stances along  over  the  surfaces  of  mucous  membranes  lining 
many  of  the  passages  and  tubes  of  the  body.  The  character 
of  the  movement  of  the  cilia  is  different  in  the  case  of  differ- 
ent cells ;  in  general  four  different  kinds  of  movement  are 
described,  viz.,  hook  form,  pendular,  wave-like,  funnel  form. 
The  movement  of  the  little  protoplasmic  process  is  generally 
regarded  to  be  a  result  of  contractility,  the  contraction  being 
rapid  and  the  recovery  being  somewhat  slower;  opinions 
differ,  however,  as  in  the  case  of  muscles,  with  regard  to 
the  internal  forces  and  method  of  action  of  the  cell.  The 
contractions  follow  each  other  too  rapidly  to  be  followed  by 
the  eye;  Engelmann  estimated  the  rate  of  vibration  of  the 
cilia  of  the  mucous  membrane  of  the  esophagus  of  the  frog 
to  be  twelve  per  second.  As  the  cell  begins  to  die,  however, 
the  movements  slow  and  the  phenomenon  can  be  studied. 
Like  all  forms  of  protoplasm,  the  cilia-bearing  cells  have  con- 
ductivity, and  this  may  persist  after  contraction  has  ceased. 
The  waves  of  activity  take  a  definite  course  across  a  ciliated 
mucous  membrane,  and  when  watched  under  a  microscope, 
call  to  mind  the  effect  of  wind  blowing  across  a  field  of 
grain.  The  harmonious  action  of  the  cells  of  a  membrane 
to  move  substances  over  the  surface,  suggests  the  passage 
of  a  peristaltic  wave  along  the  intestine.  In  spite  of  their 
microscopic  size,  the  combined  action  of  the  cilia  enables 
them  to  accomplish  considerable  work,  and  it  has  been  esti- 
mated that  one  square  cm.  can  move  a  load  of  330  grams. 
The  rate  of  action  is  influenced  by  temperature ;  weak  acids 
at  first  excite,  and  later  slow  and  destroy  action ;  slight 
alkalinity  favors  activity. 

ExPilRiMRNT.     Pith  the  brain  and  the  spinal  cord  of  a 
frog;  cut  through  the  middle  of  the  lower  jaw,  and  extend 


196  EXPERIMENT   XXXIV. 

the  incision  down  the  esophagus  to  the  stomach;  divide 
this,  and  carefully  dissect  off  the  esophagus,  pharynx,  and 
part  of  the  mucous  membrane  of  the  mouth ;  pin  the  edges 
to  a  sheet  of  cork,  so  as  to  obtain  a  level  field  with  the 
inner  surface  uppermost.     Rinse  with  normal  salt  solution. 

a.  Work  of  Cilia. 

By  means  of  pins  fasten  two  threads  across  the  mem- 
brane, one  cm.  apart,  and  a  short  distance  above  it.  Put 
a  small  piece  of  cork  on  the  membrane  and  see  in  which 
direction  it  will  be  carried  along,  toward  or  away  from 
mouth  end.  Cut  some  small  flat  pieces  of  lead,  and  find 
what  is  the  greatest  weight  which  can  be  moved  by  a  given 
surface  of  membrane.  Tilt  the  cork  plate  and  see  if  the 
weights  will  be  carried  up  hill. 

b.  Effect  of  Temperature. 

Test  the  rate  at  which  the  small  piece  of  cork  will  be 
moved  when  the  membrane  is  at  room  temperature,  when  it 
is  cooled  and  when  it  is  warmed.  (The  temperature  can  be 
<:hanged  by  placing  sheet  of  cork  with  the  membrane,  in  the 
dish  which  will  be  provided,  and  by  flowing  over  the  mem- 
brane normal  salt  solutions  which  are  ice-cold,  warmed  to 
25°  C,  and  to  50°  C.) 

€.     Microscopic  Examination  of  Cilia. 

Remove  a  few  cells  from  the  membrane  by  gently  scrap- 
ing it;  put  them  in  a  drop  of  salt  solution  on  a  slide,  and 
study  the  movements  of  the  cilia  under  a  microscope.  Re- 
port the  results  of  the  above  experiments  in  your  notes. 


crrjA. 


197 


igS  KXPKRIMENT  XXXIV. 


ARTERIAI,   PRESSURE    IX    MAN.  I99 


HXPERHJEXT  XXXV. 

Measurement  of  Systolic  and  Diastolic  Pressure  in  Hu- 
man Arteries. 

The  blood  pressure  is  a  measure  of  the  potential  energy 
available  for  overcoming  the  resistance  offered  by  the  walls 
of  the  vessels  to  the  flow  of  the  blood.  The  arterial  pres- 
sure at  a  given  point  depends  on  the  amount  of  blood  being 
pumped  by  the  heart,  the  condition  of  the  arterial  walls,  and 
the  resistance  to  the  passage  of  the  blood  through  the  small 
arteries,  capillaries,  and  veins  of  the  body  as  a  whole,  and 
of  the  artery  where  the  pressure  is  to  be  measured.  Since  a 
high  pressure  means  excessive  work  for  the  heart,  and  since 
a  low  pressure  means  too  little  blood  is  being  pumped,  or 
that  the  vessels  are  abnormally  dilated,  it  is  evident  that  a 
measure  of  the  blood  pressure  is  of  great  clinical  importance. 
In  practice,  it  is  assumed  that  the  pressure  of  the  blood  in 
the  brachial  can  be  taken  as  a  measure  of  the  condition  of 
the  general  blood  pressure. 

It  is  necessary  to  consider  three  forms  of  blood  pressure. 
During  every  systole,  the  heart  drives  blood  into  the  arteries, 
and  at  some  time  during  the  systole  the  maximal  pressure 
for  that  beat  is  reached,  and  this  would  be  the  systolic  pres- 
sure for  that  cycle.  During  the  diastole  of  the  ventricle,  the 
blood  flows  out  of  the  peripheral  end  of  the  arteries  into 
the  capillaries,  and  just  at  the  close  of  the  diastole  the 
minimal  pressure  for  that  beat  is  reached,  and  this  would  be 
called  the  diastolic  pressure  for  that  cycle.  The  pulse  pres- 
sure for  a  gii'en  cycle  is  that  which  is  added  to  the  diastolic 
pressure,  by  the  systolic  injection  of  blood  into  the  arteries. 
The  systolic  pressure  for  an}"-  beat  is,  therefore,  the  sum  of 
the  diastolic  and  pulse  pressures  for  that  beat. 

In  as  much  as  the  general  arterial  pressure  is  changing 
from  moment  to  moment,  showing  respiratory  and  Traube- 
Hering  waves,  the  individual  pulse  beats  must  be  thought  of 
as  superposed  on  these  waves.     The  general  systolic  pres- 


200  EXP1?;RIMKNT    XXXV. 

sure  would  be  the  highest  pressure  reached  during  any  beat 
on  the  crest  (jf  the  highest  blood  pressure  wave,  and  the 
general  diastolic  pressure,  the  lowest  pressure  reached  dur- 
ing any  beat  in  the  trough  of  the  lowest  blood  pressure  wave. 
The  general  pulse  pressure  would  have  to  be  considered  as 
the  average  of  the  pulse  pressures  of  the  separate  beats 
occurring  during  the  time  that  the  pressure  was  being 
studied,  and  should  be  called  the  "average  pulse  pressure/' 

The  lateral  expansion  of  the  wall  of  an  artery  by  the 
blood  pressure  is  resisted  by  the  elastic  forces  of  the  wall. 
If  the  diastolic  pressure  is  low,  the  wall  is  lax,  and  can  be 
distended  by  the  pressure  added  by  each  systole,  and  will 
contract  during  the  next  diastole.  In  this  case,  slight  oscil- 
lations of  the  wall  may  occur.  If  the  diastolic  pressure  is 
high,  or  even  normal,  the  wall  will  be  kept  so  much  stretched 
all  the  time,  that  the  added  pressure  of  a  systole  will  not 
distend  it  much,  and  the  pulse  oscillations  of  the  wall  will 
not  'be  large  enough  to  be  detected  by  the  eye.  Nevertheless, 
there  will  be  oscillations  of  pressure  which  can  be  felt  by  the 
finger  pressing  on  the  artery,  or  by  a  suitable  apparatus. 

Apparatus. — A  sphygmomanometer  is  an  instrument  de- 
vised to  measure  more  accurately  than  the  finger,  the  systolic 
and  diastolic  pressures.  Quite  a  variety  of  forms  of  this 
apparatus  are  now  used  in  practice.  The  one  employed  in 
the  laboratory,  is  a  modification  of  the  Erlanger  apparatus, 
(see  Fig.  39).  It  consists  of  a  wide  rubber  bag  which  is 
placed  on  the  inside  of  the  upper  arm  over  the  site  of  the 
brachial  artery,  and  is  held  in  place  by  an  inelastic  leather 
cuff ;  a  tube  from  the  bag  communicates  with  an  air-pump, 
to  blow  it  up,  and  raise  the  pressure  which  is  to  compress 
the  artery  :  a  manometer  to  register  the  amount  of  pressure ; 
a  fine  leak,  to  let  the  pressure  fall  gradually ;  a  larger  leak  to 
let.  the  air  out  quickly.  The  air  system  is  also  connected 
with  a  distensible  rubber  bulb,  enclosed  in  a  flask,  and  the 
air  in  this  flask  communicates  with  a  delicate,  magnifying 
tambour ;  the  arrangement  is  such  that  the  pulsations  of  the 
air  in  the  bag  over  the  artery  are  imparted  to  the  bulb  in 
the  flask,  and  through  this  to  the  surrounding  air,  and  by 
means  of  this  to  the  tambour. 


ARTEIiTAL   PRESSURE:   IN    MAN. 


20I 


Method  of  Measuring  the  Systolic  and  Diastolic  Pres- 
sure.— The  usual  method  is  to  compress  the  artery,  by  forcing 
air  into  the  bag  until  the  manometer  registers  a  pressure  of 
140  mm.,  or  more,  of  mercury,  one  sufficient  to  stop  the 


Fig.  39.  A  laboratory  form  of  sphygmomanometer.  C,  arm  bag;  P, 
pump;  M,  mercury  manometer;  L,  small  leak;  I,  cock  to  shut  off 
pump ;  2,  cock  to  shut  off  adjustable  leak ;  4,  clamp  at  large  outlet ; 
B,  bulb  expanding  and  contracting  as  pressure  changes ;  T,  magni- 
fying tambour  recording  pulse  oscillations  of  bulb  ;  3,  clamp  controll- 
ing   outlet   of   tambour 


flow  of  blood  through  the  artery,  and  then  to  let  the  air 
escape  from  the  system  through  a  fine  leak ;  at  the  same  time 
the  pressures  shown  by  the  manometer  are  watched,  and  the 
pulse  movements  of  the  tambour  are  recorded.  Several 
different  criteria  have  been  adopted  as  indicating  when  the 
systolic  and  diastolic  pressures  have  been  reached. 


202  EXPERIMENT    XXXV. 

I.  Systolic  Pressure.  The  pressure  at  which  the  blood 
breaks  through  beneath  the  bag,  is  considered  the  systoHc 
pressure.  But  ail  the  criteria  indicating  that  the  blood  has 
forced  its  way  beneath  the  bag,  give  inconstant  results  at 
the  critical  point,  because  the  pressure  of  the  blood  is  under- 
going respiratory  variations,  and  with  every  rise  of  blood 
pressure,  the  pulse  wave  breaks  through,  and  during  the 
succeeding  fall,  fails  to  pass.  The  Traube-Hering  waves  of 
blood  pressure  exert  a  similar  influence,  and  add  to  the  diffi- 
culty of  determining  the  systolic  pressure  with  exactness. 
Nevertheless  the  pressure  can  be  usually  measured  with, 
sufficient  accuracy  for  practical  needs. 

a.  Tactile  Criterion.  Shortly  after  the  pulse  breaks 
through,  it  may  be  felt  by  the  finger  at  the  wrist. 

b.  ^-Auscultatory  Criterion.  Soon  after  the  pulse  begins  to 
pass  the  bag,  one  can  hear  with  a  stethoscope  placed  on  the 
skin  over  the  artery  just  distal  to  the  bag,  a  series  of  low 
tones  caused  by  the  pulse  wave  acting  on  the  collapsed  ar- 
tery. At  first,  faint,  clear  tones,  or  even  clicks,  are  heard; 
these  are  followed  by  faint  murmurs,  or  a  roughening  of  the 
sound ;  then  a  louder,  clear  sound  may  be  heard  again ;  and 
finally  softer  sounds  which  fade  away.  Periodic  variations 
in  the  arterial  pressure  nia)^  cause  the  first  of  these  sounds 
to  disappear  and  to  reappear,  also  the  rate  at  which  the  pres- 
sure falls  in  the  bag  may  influence  the  duration  and  quality 
of  the  sounds.  The  systolic  pressure  should  be  read  when 
the  first  sound  is  heard,  and  diastolic  pressure  at  the  point 
where  all  sounds  suddenly  become  less. 

c.  Criterion  of  a  Sudden  Rise  of  Pulse  Record.  When  the 
air  is  forced  into  the  bag,  the  pressure  in  the  bag  acts  with 
the  elastic  force  of  the  arterial  wall  to  overcome  the  pres- 
sure of  the  blood  in  the  artery.  As  the  walls  of  the  artery 
are  forced  together,  the  elasticity  of  the  wall  of  the  artery 
plays  less  and  less  part,  and  finally  the  pressure  in  the  bag 
alone  opposes  the  pressure  of  the  blood  in  the  vessel.  If 
the  pressure  is  raised  sufficiently  to  overcome  the  highest 
pressure  in  the  artery,  and  prevents  the  blood  from  entering 
the  part  of  the  vessel  under  the  bag,  the  bag  pressure  would 
be  greater  than  systolic,   (see  I,  Fig.  40)   and  in  this  case 


ARTEEIAI,   PRl-SSURE   IN    MAN. 


20' 


?..(TH 


SDP 


iin 


N\^^.^K^^ 


J  15 


iz 


there  would  be  no  pulse  oscillations  of  pressure  in  the  air  in 
the  bag,  except  very  small  pulsations,  caused  by  the  end 
of  the  compressed  artery  beating  against  the  side  of  the  bag. 

If  now  the  pressure  is 
lowered  very  gradually,  the 
blood  will  begin  to  w^ork 
into  the  artery  beneath  the 
bag,  (see  II,  Fig.  40).  Von 
Recklinghausen  pointed  out 
that  if  the  pressure  in  the 
bag  falls  moderately  rapid- 
ly, there  usually  comes  quite 
a  sudden  rise  in  the  height 
of  the  recorded  pulse  beats, 
at  the  instant  that  the  blood 
forces  its  way  into  the  part 
of  the  artery  under  the  bag, 
and  when  this  occurs  it 
would  seem  to  be  a  good  in- 
dication of  the  systolic 
pressure. 

d. .  .  Criterion  of  Separation 
of  the  Ascending  and  De- 
scending Limbs  of  the 
Pulse  Curvc.^  Another  piece 
of  evidence  is  to  be  found 
in  the  shape  of  the  pulse 
obtained  with  the  tambour. 
Erlanger  states  that  if  the 
record  be  taken  on  a  drum 
moving  not  too  slowly,  at 
the  moment  that  the  pulse  beats  begin  to  work  under  the 
bag,  the  up  and  down  strokes  are  to  be  seen  to  separate,  and 
that  this  separation  is  to  be  taken  as  the  criterion  for  the 
systolic  pressure. 

II.     Diastolic  Presure. 

a.  The  Auscnlatory  Criterion.  The  sudden  lessening  of 
the  sounds  heard  over  the  artery,  distal  to  compression  of 
the  bag.  as  the  pressure  in  the  bag  falls. 


°,  A  iyviv4v,LQ':-^^>~j;^-sf  ststKf? 


"i 


Fig.  40.  Diagram  showing  how 
varying  pressures  in  the  bag,  by  act- 
ing against  the  systoHc,  diastolic,  and 
pulse  pressures,  alter  the  tension  of 
the  wall  of  the  artery,  and  consequent- 
ly the  pulse  oscillations  of  the  air  in 
the  bag  and  the  tambour  record.  A, 
artery;  B,  bag;  D,  diastolic  pressure; 
S,  systolic  pressure ;  _P,  pulse  pressure  ; 
I,  pressure  in  bag  is  more  than  sys- 
tolic ;  II,  pressure  in  bag  is  less  than 
systolic,  and  more  than  diastolic ;  III, 
pressure  in  bag  is  diastolic ;  IV,  pres- 
sure in  bag  is  less  than   diastolic. 


204  f:xpe;rimf,nt  xxxv. 

b.  The  Largest  Pulsation  Criterion.  As  the  pressure 
in  the  bag  is  lessened,  the  recorded  pulsations  of  the  air  in 
the  bag  grow  in  height,  till  a  certain  maximum  is  reached, 
and  then  begin  to  decrease.  How  is  this  to  be  explained? 
After  the  blood  has  worked  into  the  artery  beneath  the  bag, 
the  amount  that  the  wall  of  the  artery  is  stretched  by  the 
pressure  of  the  blood  during  S3^stole  and  diastole,  depends 
on  the  amount  of  the  pressure  in  the  bag  plus  the  elastic 
resistance  of  the  wall  of  the  artery,  on  the  one  hand,  and 
on  the  amount  of  pressure  in  the  blood  during  systole  and 
during  diastole,  on  the  other.  As  the  pressure  in  the  bag 
falls,  the  arterial  wall  gradually  losing  this  support,  is 
stretched  more  and  more,  and  has  to  sustain  more  of  the 
blood  pressure.  As  the  pressure  in  the  bag  continues  to 
lessen,  a  point  is  reached  when  the  pulsations  recorded  by 
the  tambour  are  greatest,  (See  I,  II,  III,  Fig.  40.)  At  this 
point  the  pressure  in  the  bag  is  just  able  to  overcome  the 
pressure  in  the  artery  at  the  time  the  pressure  is  diastolic, 
but  not  able  to  overcome  the  systolic  pressure,  therefore, 
the  air  pressure  in  the  bag  oscillates  between  the  diastolic 
pressure  and  the  pressure  caused  by  the  distension  of  the 
artery  during  systole.  TJte  pressure,  at  which  the  greatest 
pulsations  are  seen,  is  considered  the  diastolic  pressure. 

As  the  pressure  in  the  bag  falls  further,  the  elasticity  of 
the  wall  of  the  artery  is  called  on  more  and  more  to  resist 
the  diastolic  pressure,  and  the  air  in  the  bag  is  subjected 
less  and  less  to  the  systolic  presure.  (See  IV,  Fig.  40.) 
For  a  considerable  time,  however,  the  pressure  in  the  bag 
aided  by  the  elasticity  of  the  wall  of  the  artery  can  equal 
the  diastolic  pressure,  and  the  pulsations  of  the  tambour 
can  show  the  diastolic  part  of  the  curve,  although  the  wall 
of  the  artery  resisting  the  systolic  pressure  more  and  more, 
the  air  in  the  bag  is  affected  less  by  this,  and  the  tambour 
tracing  shows  less  and  less  of  the  s3'stolic  part  of  the  curve. 

As  the  pressure  in  the  bag  falls  still  lower,  the  elastic 
wall  has  to  support  the  blood  pressure  still  more,  and  the 
pressure  in  the  bag  and  the  movements  of  the  tambour  fail 


AKTKKIAL  PRESSURE  IN  MAN.  205 

more  and  more  to  follow  the  diastolic  part  of  the  curve, 
and  finalty  the  arterial  wall  alone  acting  against  the  pres- 
sure in  the  artery  during  diastole,  no  movement  of  the  tam- 
bour will  be  seen. 

EXPERIMENT. 

I.     Systolic   Pressure,   as  Determined    by   a   Pulse   at   the 
Wrist  (Tactile  Criterion). 

First  become  familiar  with  the  apparatus,  (see  Fig.  39), 
and  its  method  of  operation.  The  leak  tube  L  has  been  ad- 
justed so  that  the  mercury  in  the  manometer  will  fall  at 
such  a  rate  that  the  pressures  can  be  easily  read  for  every 
5  mm  on  the  scale,  i.  e.,  for  every  10  mm  fall  of  pressure. 

a.  Subject  seated.  Open  clamp  3,  (this  is  to  be  always 
open  except  when  records  from  the  tambour  are  required). 
The  subject  should  be  seated  and  quiet,  the  left  arm  being 
flexed  at  a  right-angle,  and  the  forearm  being  supported  by 
a  sling.  Strap  the  bag  over  the  site  of  the  left  brachial  ar- 
tery and  see  that  it  is  wholly  covered  by  the  leather  cuff. 
Examine  the  pulse  in  the  wrist,  so  as  to  be  sure  of  the  point 
where  it  is  felt  most  strongly.  Open  the  cock  I  (on  the 
tube  connecting  with  the  pump)  and  close  cock  2,  (on  leak 
tube)  and  close  clamp  4,  (on  outlet  tube).  Raise  pressure 
in  bag  by  pumping  until  mercury  in  manometer  stands  at 
140  mm.,  i.  e.,  70  mm.  on  the  scale.  Then  close  cock  i,  and 
open  cock  2.  With  nnger  on  wrist,  watch  the  fall  of  the 
mercury  and  note  the  exact  point  at  which  the  first  pulse 
beat  is  detected.     Five  good  readings  are  required. 

b.  Subject  standing. 

Determine  the  systolic  pressure  with  the  arm  in  same 
position  as  in  a.  Be  ready  to  take  the  reading  as  soon  as 
the  subject  gets  up,  and  continue  to  take  readings  at  regu- 
lar, short  intervals.     Five  good  readings  required. 

c.  B,ifect  of  Exercise. 

The  subject  is  to  run  rapidly  down  and  up  stairs.  The 
cuff  is  to  be  detached  from  the  instrument,  and  is  to  be  worn 


2o6  EXPERIMENT   XXXV. 

during  the  run.  The  readmgs  are  to>  be  taken  as  soon  after 
the  run  as  is  compatible  with  accuracy.  Five  readings 
should  be  taken  at  regular  short  intervals. 

Notes. 

The  figures  obtained  in  the  three  cases  and  their  aver- 
ages are  to  be  recorded  in  the  notes,  together  with  explana- 
tions of  the  differences  observed. 

II.  Systolic  and  Diastolic  Pressures  by  the  Auscultatory 

'  Method. 
The  experiment  is  to  be  made  when  the  subject  is  in  the 
sitting  position,  and  in  the  same  way  as  in  a  of  the  preced- 
ing section,  except  that,  instead  of  the  pulse  at  the  wrist 
being  taken,  the  sound  given  out  by  the  artery  below  the 
cuff  as  the  pulse  beats  enter  it,  is  to  be  listened  for.  A 
stethoscope  is  to  be  used  to  hear  the  sounds  (use  your  own 
if  possible;  if  forced  to  use  another,  see  that  the  ear  pieces 
are  well  cleaned.)  The  first  sound  heard,  is  a  clear  sound, 
often  a  distinct  click ;  later,  the  sounds  are  roughened,  or  are 
more  like  murmurs,  with  perhaps  some  clear  sounds  inter- 
spersed; and  finally  clear  sounds  are  again  heard  and  these 
gradually  fade  away.  Five  tests  are  to  be  made.  Let  sev- 
eral minutes  elapse  between  the  tests,  to  permit  the  effects 
of  congestion  to  pass  off. 

a.  Systolic  Pressure. 

The  manometer  is  to  read  at  the  instant  that  the  first 
pulse  beat  is  heard.     This  marks  the  systolic  pressure. 

b.  Diastolic  Pressure. 

A  second  reading  is  to  be  taken  at  the  moment  the 
sounds  are  fading  away.    This  marks  the  diastolic  pressure. 

III.  Systolic    and    Diastolic    Pressures    by    the    Tambour 

'Method. 

Arrange  a  time  signal  to  write  in  the  same  vertical  line 

and  beneath  the  lever  of  the  tambour,  and  connect  the  signal 

in  the  circuit  with  a  Morse  key  and  a  dry  cell.    The  subject 

is  to  sit  quietly.     The  apparatus  is  to  be  used  as  before, 


ARTliRIAI,   PRKSSURE   IN    MAN.  207 

except  that  the  outlet  from  the  tambour,  cock  3,  (see  Fig. 
39)  is  to  be  closed,  so  that  the  pulsations  of  the  air  about 
the  bulb  in  the  bottle  will  be  communicated  to  the  tambour. 
Record  on  a  drum,  running  about  5  mm  per  second,  a  curve 
of  the  movements  of  the  tambour.-  Start  with  a  pressure 
about  20  mm  above  the  systolic  pressure  found  in  the  tests 
of  the  preceding  sections.  While  the  record  is  being  taken, 
and  the  pressure  is  falling,  tap  on  the  key,  so  as  to  mark 
every  5  mm  fall  of  the  mercury  in  the  manometer,  and  give 
a  double  tap  at  the  100  and  at  the  50  mm  points. 

a.  Systolic  Pressure. 

Mark  on  the  curve  after  it  is  shellaced  the  point  when 
the  pulsations  suddenly  begin  to  increase  in  height,  (von 
Recklinghausen's  criterion).  Also  mark  the  point  when  the 
up  and  down  strokes  begin  to  separate  (Erlanger's  crite- 
rion). 

b.  Diastolic  Pressure. 

Mark  the  place  where  the  pulsations  are  greatest,  or 
rather  where  they  first  begin  to  lessen  in  height. 


208 


IsXPr^R  I M  I'.NT   XXXV. 


ARTERIAI,   PRKSSURi;   IN    MAN,  209 


IvXPERIMKNT   XXXV. 


PLETHYSMOGRAPH.  211 

EXPERIAIEXT  XXXVI. 
Conditions  Changing  the  Volume  of  Hand. 

The  size  of  the  arm  or  the  finger,  Hke  that  of  most  of 
the  organs  of  the  body,  is  continually  changing.  It  is  in- 
fluenced bv  all  conditions  altering  the  general  arterial  pres- 
sure, and  by  local  changes  in  the  blood-vessels,  and  lymph- 
atics of  the  part  itself.  If  the  arm  or  a  finger  be  enclosed 
in  an  air-tight  chamber,  and  the  chamber  be  connected  with 
a  sufficiently  delicate  recording  apparatus,  the  changes  in 
volume  can  be  Avritten  on  a  kymograph  drum.  The  record 
will  show  pulse  waves  superposed  on  respiration  waves, 
and  these  often  will  be  seen  to  be  superposed  on  Traube- 
Hering  waves. 

Changes  in  the  blood  pressure,  caused  by  vaso-constric- 
tion  or  dilation  in  other  parts  of  the  body,  especially  in  the 
abdominal  organs,  or  vaso-constriction  or  dilation  of  the 
part  itself,  will  also  change  the  height  of  the  curve.  Thus 
psychic  activity  of  an  emotional  tA^pe,  will  cause  constriction 
of  the  vessels  of  the  arm  and  a  fall  of  the  curve ;  cold  ap- 
plied to  other  hand,  through  the  eitect  of  a  crossed  reflex 
on  the  vessels  of  the  part,  will  cause  vaso-constriction  and  a 
lessened  volume. 

Apparatus. — This  consists  of  a  glass  receptacle  in  which 
the  arm  or  finger  is  placed,  the  space  between  the  end  of 
the  tube  and  the  member  being  closed  off  by  a  rubber 
sleeve.  In  the  case  of  the  finger  the  best  results  are  to  be 
obtained  by  connecting  the  chamber' with  a  delicate  piston 
recorder.  In  the  case  of  the  arm,  a  recorder  capable  of 
accommodating  larger  volumes  of  air  has  to  be  employed. 
Directions  for  the  use  of  the  apparatus  will  accompan}-  it. 

Caution. 

The  tube  leading  to  the  recorder  sJwiiId  be  kept  closed, 
and  the  tube  which  communicates  with  the  outside  air  should 
be  kept  open,  except  when  the  experiment  is  to  be  made. 


212  EXPERIMENT  XXXVI. 

The  syringe,  which  connects  with  a  side  branch  of  the 
main  tube  can  be  used  for  fine  adjustments  of  the  air  vol- 
ume in  the  chamber. 

Since  the  chamber  is  filled  with  air,  it  is  very  sensitive 
to  temperature  changes,  and  when  the  part  is  first  intro- 
duced, the  outlet  tube  must  be  left  open  until  the  system  has 
/^adjusted  to  write  below  the  recorder,  and  be  connected  with 
(    a  dry  cell  and  a  key,  so  that  the  time  of  changes  of  condi- 
^{taken  on  the  new  temperature.     A  time  signal   should  be 
tions  likely  to  influence  the  subject  may  be  registered.    The 
pain  caused  by  a  tetanizing  current  applied  to  the  skin  by 
a  dry  wire  brush  will  be  employed,  and  the  brush  should  be 
connected  with  the  secondary  coil,  ready  for  use. 

Experiment. — Good  results  are  to  be  obtained  only 
when  the  hand  is  7uarm,  for  if  the  vessels  are  constricted, 
only  very  slight  or  no  changes  in  the  volume  will  be  ob- 
served. The  subject  is  to  sit  at  ease  and  the  left  arm  or 
the  second  finger  of  the  left  hand  is  to  be  used.  See  that  the 
side  tube  is  open  and  that  the  clamp  protecting  the  recorder 
is  closed.  A  sleeve  having  been  chosen,  which  will  make 
the  opening  between  arm  or  the  finger  and  the  chamber  air- 
tight, but  without  constricting  the  vessels,  place  the  part  in 
the  chamber.  Let  the  subject  sit  quietly  while  the  air  is 
taking  on  the  new  temperature.  After  five  minutes,  open 
the  clamp  to  the  recorder,  and  then  provisionally  close  the 
outlet  by  pinching  the  tube.  The  record  should  show  pulse 
beats  and  respiration  effects.  To  obtain  the  best  results, 
the  friction  of  the  pointer  on  the  drum  must  be  reduced  to 
a  minimum.  In  case  the  record  is  rising  rapidly  again  open 
the  escape  tube,  and  wait  for  the  temperature  to  become 
adjusted.  The  drum  should  move  at  about  the  rate  of  2  mm 
per  second.  When  a  normal  quiet  record  has  been  taken, 
the  efl:"ect  of  the  following  influences  may  be  tried: 

a.     Tickling. 

Brush  the  face  lightly  with  the  corner  of  a  strip  of  paper, 
and  record  the  time,  by  pressing  on  the  key  during  the  peri- 
od of  stimulation.  The  corners  of  the  mouth  are  especially 
ticklish.     The  subject  must  avoid  movements. 


PLKTHYSMOGRAPII.  213 


b.     Pain. 


Connect  the  primary  coil  of  the  induction  apparatus  in 
the  circuit  with  the  electric  signal,  dry  cell,  and  key.  Let 
the  experimenter  test  the  strength  of  the  current  to  be  em- 
ployed by  applying  the  brush  to  the  skin  of  the  back  of  his 
own  hand,  and  increasing  the  strength  of  current  until  it 
is  decidedly  unpleasant.  Now  the  secondary  coil  should  be 
pushed  back  a  short  distance,  the  brush  applied  to  the  back 
of  the  hand  of  the  subject,  and  a  strength  of  current  found 
which  is  as  much  as  he  wishes  to  stand.  Wait  about  three 
minutes :  then  try  the  effect  when  the  drum  is  running  and 
a  good  normal  record  is  being  taken.  The  subject  must  try 
to  avoid  making  any  movements  at  the  time.  Remove  coil 
from  signal  circuit  and  restore  signal  key. 

c.  Psychic  Excitation. 

When  "quiet"  records  are  being  taken,  the  effect  of 
psychic  activity  may  be  studied  by  letting  the  subject  try  to 
multiply  47  by  82,  for  example,  and  give  the  answer  as 
quickly  as  possible.  Record  on  the  drum  the  instant  that  the 
problem  is  stated,  by  pressing  on  the  signal  key  and  keep 
it  down  until  the  instant  that  the  answer  is  given. 

d.  Cold : — 

Half  fill  a  glass  jar  with  ice  cold  water.  Place  jar  on 
floor  below  suspended  right  hand  of  subject.  After  the 
hand  has  been  in  this  position  for  two  or  three  minutes  ex- 
amine the  veins  and  make  note  of  the  color  of  the  hand. 
When  a  "quiet"  record  is  being  taken,  let  a  third  student 
raise  the  jar,  so  that  the  hand  of  the  subject  will  be  im- 
mersed. The  subject  himself  should  make  no  movement. 
Record  on  the  drum  the  instant  that  the  jar  is  raised,  and 
continue  to  press  on  the  recording  key  until  the  jar  is  low- 
ered. The  muscles  of  the  walls  of  the  vessels  are  non-stri- 
ated and  slow  to  act.  Three  or  more  seconds  are  necessary 
for  the  first  change  to  appear.  Examine  the  hand  again, 
making  note  of  the  color  of  the  hand  and  amount  of  con- 
striction of  the  veins. 


214 


KXrERIMTjNT  XXXVI. 


VENOUS  TRKSSUR];.  215 

EXPERIMENT  XXXVU. 
Venous  Pressure  in  Man. 

Under  normal  conditions,  the  pressure  of  the  blood  in 
the  veins  at  the  level  of  the  upper  border  of  the  heart  is 
very  low.  According  to  v.  Recklinghausen,  when  a  person 
is  in  the  recumbent  position,  the  level  of  the  large  veins  at 
the  point  of  entrance  intO'  the  heart  can  be  considered  to  be 
7-1 1  cm  dorsal  to  the  sternum.  If  a  normal  man  is  lying 
down  and  places  one  hand  on  the  bed  and  the  other  on  the 
thigh,  it  will  be  found,  after  the  few  minutes  required  for 
adjustment,  that  the  veins  of  the  hand  on  the  bed  are  some- 
what distended,  and  those  of  the  hand  on  the  thigh  are 
empty.  If  this  is  observed,  the  pressure  can  be  regarded 
as  normal.  In  case  the  veins  of  the  hand  on  the  thigh  are 
distended,  the  pressure  is  above  the  normal. 

Gaertner's  method  of  measuring  the  venous  pressure  re- 
quires no  apparatus  and  is  sufficiently  accurate.  In  order 
that  the  blood  may  flow  to  the  right  heart,  the  pressure  must, 
at  least,  be  equal  to  that  of  the  blood  in  the  veins  at  the 
level  of  the  upper  border  of  the  heart.  This  point,  in  the 
upright  position,  can  be  considered  to  be  at  the  height  of 
the  second  intercostal  space,  (See  Fig.  42). 

The  pressure  of  the  blood  in  the  veins  of  the  hand  at  a 
given  point  would  depend  on  the  amount  of  energy  left  in 
the  blood  after  it  had  passed  the  capillaries,  and  the  resist- 
ance which  it  would  encounter  on  its  way  to  the  heart.  This 
latter  factor  would  be  composed  of  the  resistance  of  the 
blood  pressure  in  the  veins  at  the  heart,  (which  it  is  pro- 
posed to  measure),  plus  the  weight  of  the  column  of  blood 
which  would  have  to  be  lifted,  plus  the  resistance  offered  by 
the  walls  of  the  veins.  N^eglecting  this  last  factor,  which  we 
can  not  measure,  the  pressure  of  the  veins  in  the  hand, 
minus  the  weight  of  the  column  of  blood  from  the  hand  up 
to  the  heart  level,  if  the  hand  was  lower,  or  plus  this  weight. 


2l6  EXPERIMENT  XXXVII. 

if  it  was  higher  than  the  level  of  the  heart,  would  give  the 
venous  blood  pressure  at  the  heart. 

Experiment. — Let  the  subject  sit  erect  in  a  comfortable 
position,  and  with  his  left  arm  on  the  lowered  arm  rest. 
Determine  the  height  of  the  upper  border  of  the  heart,  by- 
adjusting  the  lower  border  of  the  horizontal  meter  stick  to 
the  level  of  the  second  intercostal  space.  Raise  the  arm 
rest  to  about  lo  cm  below  this  level,  and  wait  two  minutes ; 
then,  moving  short  distances  and  waiting  two  minutes  be- 
tween each  test  ascertain  the  height  at  which  the  largest 
veins  collapse.  Measure  this  height,  and  state  in  the  notes 
the  difiference  between  this  and  the  heart  height,  and  report 
the  figures  obtained  and  the  pressure  of  the  venous  blood 
at  the  heart  in  mm  Hg.  Blood  is  5%  heavier  than  water. 
Mercury  has  13.6  times  the  weight  of  water.  Note  the  tem- 
perature of  the  room,  the  time  of  day,  and  any  other  condi- 
tions that  might  influence  the  result. 


VENOUS  prrssurf;.  217 


21! 


F,Xrr,RlMF,NT  .XXXV'II. 


Vl'NOUS  I'UJ.SK  219 

EXPERIMENT  XXXVIII. 
The  Pulse  in  the  Large  Veins  of  Man. 

The  pulse  detected  in  the  large  veins  of  the  neck  is  of 
great  clinical  interest  because  it  gives  information  with  re- 
spect to  the  action  of  the  right  auricle  and  ventricle,  just  as 
the  arterial  pulse  gives  information  concerning  the  left  ven- 
tricle. Before  trying  to  obtain  a  record  of  the  pulse,  study 
the  diagram  in  Fig.  41,  so  as  tO'  know  the  form  of  the  curve 
to  be  sought,  and  its  relation  to  the  carotid  pulse,  and  to  the 
systole  and  diastole  of  the  right  auricle  and  ventricle. 

•  Apparatus. — The  venous  pulse  is  recorded  by  an  open 
tambour,  or  one  closed  by  a  thin,  loose,  rubber  membrane, 
connected  with  a  delicate,  magnifying,  recording  tambour; 
the  carotid  pulse  is  recorded  as  in  Experiment  XXX.  From 
the  start,  both  of  the  recording  tambours  must  be  adjusted 
so  that  their  levers  are  horizontal,  i.  e.,  with  the  writing 
points  on  a  level  with  the  axes.  The  length  of  each  lever 
is  to  be  measured,  after  it  has  been  applied  to  the  drum  in 
the  position  in  which  it  is  to  write.  Place  a  fork  so  as  to 
write  below  the  two  levers. 

Experiment. — Let  the  subject  lie  on  his  back,  and  seek 
the  A^enous  pulse  by  applying  the  receiving  tambour  to  vari- 
ous points  over  the  veins  of  the  neck,  avoiding  only  the  re- 
gion over  the  carotids.  Try  first  over  the  external  jugular. 
Occasionally  a  good  pulse  is  got  by  deep  pressure  in  the 
supra-sternal  notch.  The  position  of  the  head  is  important, 
and  often  various  positions  must  be  tried  before  one  suita- 
ble to  the  subject  will  be  found.  The  muscles  of  the  neck 
should  be  relaxed,  and  conditions  favorable  to  a  large  flow 
of  venous  blood,  such  as  a  warm  room,  are  desirable.  The 
best  result  is  usually  obtained  by  a  low  heart  rate.  When 
a  pulse,  at  least  5  mm  high,  and  evidently  different  from 
that  to  be  expected  from  a  carotid,  has  been  obtained,  ap- 
ply a  tambour  over  the  opposite  carotid  and  record  simultan- 
eously the  venous  and  arterial  tracings,  and  the  vibrations  of 


220  F.XPI;RIMKNT  XXXVIII. 


DESCRIPTION  OP  PIGURK  4I. 

Diagram  showing  relations  of  changes  in  size  of  the 
right  auricle  and  ventricle,  to  the  venous  pulse,  carotid  pulse, 
time  of  heart  sounds,  and  time  of  closure  of  valves.  I,  ven- 
ous pulse  curve;  TI,  carotid  pulse  curve;  III,  changes  in 
size  of  auricle  and  venticle ;  x — x,  resting  position  of  floor 
of  auricle;  IV,  duration  of  systole  of  auricle  and  ventricle; 
A.S.,  auricular  systole;  V.S.,  ventricular  systole;  A.D.,  auri- 
cular diastole ;  V.D.,  ventricular  diastole ;  V,  time  of  heart 
sounds,  first,  second,  and  third ;  VI,  time  of  opening  and 
closing  of  valves;  tc  and  mc,  tricuspid  and  mitral  close;  ao 
and  pOj  aortic  and  pulmonary  open ;  ac  and  pc,  aortic  and 
pulmonary  close;  to  and  mo,  tricuspid  and  mitral  open;  A, 
pos,  first  positive  wave  of  venous  pulse,  caused  by  auricular 
systole ;  A,  neg,  first  negative  wave,  caused  by  auricular 
diastole;  S,  pos,  second  positive  wave,  caused  b}^  protrusion 
of  tricuspid  valve  into  auricle,  at  beginning  of  ventricular 
systole ;  S,  neg,  second  negative  wave,  caused  by  descent  of 
floor  of  auricle :  O,  first  onflow  wave,  caused  by  accumula- 
tion of  blood  in  the  veins ;  V,  pos,  third  positive  wave, 
caused  by  return  of  floor  of  auricle  at  beginning  of  ventri- 
cular diastole;  V,  neg,  third  negative  wave,  caused  by  fill- 
ing of  ventricle  ;  h,  second  onflow  wave,  caused  by  accumu- 
lation of  blood  in  the  veins. 


VENOUS  PUI.SK 


221 


II 


IIIX 


IV 


VI 


Fig.  41.  Diagram  showing  relations  of  changes  in  size  of  the  right  auricle 
and  ventricle^  to  the  venous  pulse,  carotid  pulse,  time  of  heart  sounds,  and 
lime  of  closure  of  valves. 


222  EXPERIMENT  XXXVIII, 

the  fork.  At  the  instant  that  the  tracing  is  to  he  taken,  let 
the  subject  cease  to  breathe  at  the  end  of  a  quiet  expiration. 
He  must  merely  avoid  taking  the  next  breath,  and  not  strain. 
Do  not  fail  by  each  test,  to  mark  on  the  drum  the  exact  po- 
sition of  the  writing  points,  by  recording  large  arcs.  Also 
record  base  lines  by  revolving  the  drum  when  the  side  tubes 
are  open  and  the  levers  horizontal. 

Analysis  of  Ciirves. 

First  make  sure  that  each  of  the  levers  was  horizontal 
when  the  base  lines  were  written,  by  applying  dividers,  ad- 
justed to  the  length  of  the  lever,  to  the  base  line,  and  seeing 
whether  it  will  describe  the  arc  as  written.  Do  not  deface 
the  arc  in  the  process.  Then  draw  a  vertical  line,  just  tan- 
gent to  one  of  the  arcs,  to  ascertain  the  relative  position  of 
the  writing  points.  Now  draw  an  arc  from  the  beginning 
of  each  of  the  positive  and  negative  waves  of  the  venous 
pulse  curve,  and  from  the  beginning  of  the  rise  of  the  pri- 
mary wave  and  from  the  bottom  of  the  dicrotic  notch  of 
the  carotid  pulse  to  the  respective  base  lines.  Perpendic- 
ulars may  now  be  drawn  down  tO'  the  fork  curve,  from  the 
points  the  time  relations  of  which  are  to  be  compared. 

For  laboratory  purposes,  at  least,  it  is  best  to  use  the 
above  method,  but  many  physicians  find  it  simpler,  when 
the  relative  position  of  two  points  on  two  curves  is  to  be 
studied,  instead  of  drawing  perpendiculars,  to  measure  with 
dividers  the  distance  between  the  point  where  the  arc  from 
one  of  them  intersects  its  base  line,  and  the  starting  point 
arc,  and  then  to  la}^  off  this  distance  on  the  other  base  line, 
from  the  starting  point  arc  drawn  by  the  other  lever.  In 
any  case  arcs  must  be  drawn  from  the  parts  of  the  curves 
to  be  considered,  to  the  respective  base  lines. 

Notes. — ^State  whether  in  your  record  the  S  wave  began 
to  rise  at  the  same  time  as  the  primary  carotid  wave,  and  if 
not,  wh}^  What  was  the  relation  of  the  V  wave  to  the  de- 
scending limb  of  the  dicrotic  notch?  Explain.  Determine 
the  time  interval  betv/een  the  beginning  of  the  rise  of  the  A 
and  the  S  waves.  This  is  approximately  the  time  taken  for 
the  conduction  of  the  impulse  through  the  auricle  to  the 
ventricle. 


NORMA!,  SOUNDS  OP  HEART. 


223 


EXPERIMENT  XXXIX. 
The  Normal  Sounds  of  the  Heart. 


The  normal  heart  sounds  may  be  heard  with  the  unaided 
ear,  but  the  stethoscope  is  commonly  used.     It  consists  es 


Fig.  42.  Diagram  showing  position  of  heart  in  chest,  position  of  valves  as 
projected  on  the  wall  of  the  chest,  and  the  parts  of  the  chest  where  the  sounds 
of  the  heart  are  heard  best.  M,  position  of  apex  beat,  and  sound  from  mitral 
valve ;  T,  sound  from  tricuspid  valve ;  A,  sound  from  aortic  valve ;  P,  sound 
from   pulmonary   valve. 

sentially  of  a  receiving  disk  and  a  pair  of  ear-tubes,  con- 
nected by  tubing.  It  aids  by  multiplication  of  the  sound 
and  by  excluding  outside  sounds.     Distracting  noises,  to  be 


224  EXPEJRIMKNT  XXXIX. 

avoided,  are  apt  to  arise  from  (i)  rubbing  of  tubes  against 
each  other  or  against  clothing,  (2)  breathing  by  the  Hstener 
upon  the  metal  spring  holding  the  ear-tubes,  (3)  movement 
of  the  receiving  disk  upon  the  skin,  (4)  movements  or 
breath  sounds  of  the  subject,  and  (5)  talking  by  either  sub- 
ject or  listeners.  The  multiple  instrument  enables  several 
persons  to  hear  the  same  sound  at  once,  and  therefore  is 
useful  in  teaching.  The  ear  tubes  should  be  cleansed  before 
inserting  them  for  the  first  time,  to  avoid  possible  infection. 
The  tubes  are  placed  in  the  ears  with  the  tips  pointing  in- 
ward and  upward.  The  receiving  disk  is  held  firmly  against 
the  skin.    Avoid  kinks  in  the  rubber  tubes. 

Figure  42  shows  the  position  of  the  heart  in  the 
chest,  and  the  letters,  A^  P,  T,  and  M  mark  the  areas  where 
the  disk  is  placed  in  listening  to  the  separate  valve  sounds. 
Each  letter  is  connected  by  a  dotted  line  with  a  dark  spot 
showing  the  position  of  the  corresponding  valves.  These 
four  areas,  knov/n  as  the  aortic,  pulmonary,  tricuspid,  and 
mitral  areas,  are  so  named  because  the  sounds  made  by  the 
closure  of  the  valves  named  are  heard  best  in  those  places, 
but  it  must  be  remembered  that  no  one  of  the  valve  sounds 
can  be  isolated  at  any  point,  but  that  all  enter  into  the  com- 
posite sounds  heard  at  each  area.  It  is  the  relative  loudness 
of  particular  sounds  that  give  the  areas  the  nam.es  which 
the}^  bear. 

a.     Auscultation  over  the  Lower  Part  of  the  Chest. 

One  student  of  the  group  is  chosen  as  subject,  and  he 
seats  himself  in  a  chair,  the  others  seating  themselves  closely 
around  him.  The  receiving  disk  is  first  applied  over  the 
mitral  area,  viz.,  at  the  point  where  the  apex  beat  is  felt,  in 
the  5th  intercostal  space,  slightly  within  the  nipple  line. 
With  the  disk  in  this  position,  listen  to  the  heart  sounds  for 
several  minutes.  Observe  (i)  the  two  distinct  sounds  with 
a  ver}-  short  interval  between  them,  (2)  the  greater  loudness 
of  the  first  sound,  (3)  the  booming  character  of  the  first 
sound  contrasted  with  the  sharp  click  of  the  second.  The 
-first- sound,  which  marks  the  beginning  of  the  systole  of  the 
ventricle,  is  a  compound  sound,  composed  of  the  click  caused 


NORMAL  SOUNDS  OF   HEART.  225 

by  the  closure  of  the  two  aitricnlo-ventricular  valves,  the 
sound  made  by  the  contraction  of  the  muscular  substance  of 
the  two  ventricles,  and  by  the  vibrations  of  the  suddenly 
tensed  chorda;  tendine?e.  The  muscular  element  which  pro- 
longs the  sound  into  the  period  of  systole,  helps  to  give  it 
the  booming  character.  Normally  the  two  ventricles  con- 
tract together,  and  the  mitral  and  tricuspid  valves  close  at 
the  same  instant,  so  that  the  action  of  the  two  sides  of  the 
heart  is  represented  by  a  single  sound.  Compare  it  with  the 
sound  heard  by  placing  the  disk  of  the  stethoscope  on  the 
muscle  of  the  forearm  and  causing  it  to  contract  rhythmic- 
ally. The  second  sound  is  produced  by  the  closure  of  the 
aortic  and  pulmonary  semi-lunar  valves,  which  normally 
close  at  the  same  time.  Now  apply  the  disk  over  the  tri- 
cuspid area  and  observe  (i)  the  greater  prominence  of  the 
valve  sound  and  lessened  muscle  sound,  (2")  the  clear  and 
high  pitched  quality  of  the  sound,  (3)  the  comparative  loud- 
ness of  the  first  sound  as  before,  and  (4)  the  rhythm,  which 
is  also  the  same  as  in  the  mitral  area.  Change  the  disk 
quickly  from  one  of  these  two  areas  to  the  other,  so  as  to 
bring  out  distinctly  the  differences  in  the  sounds.  Apply  it 
at  intermediate  points  and  observe  how  the  characteristic 
sounds  of  one  area  gradually  shade  off  into  those  of  the 
other. 

h.     Auscidtation.  over  the  Base  of  the  Heart. 

Apply  the  disk  over  the  aortic  area  and  observe  ( i)  the 
greater  loudness  of  the  second  sound  as  compared  with  the 
first,  (2)  almost  complete  absence  of  booming  muscle  sound, 
(3)  the  same  rhythm  as  before.  The  sounds  heard  here  are 
mostly  valvular,  and  the  aortic  sounds  predominate.  Listen 
in  same  manner  at  pulmonary  area,  and  compare  the  sounds 
heard  in  aortic  and  pulmonary  areas.  Move  the  disk  to  the 
four  areas  in  turn,  and  let  the  listeners  try  to  recognize  the 
area  by  the  sounds  heard.     Use  each  student  as  subject. 

In  diagnosis  it  is  often  necessary  to  locate  an  abnormal 
sound  in  relation  to  the  pulse  beat  and  thence  to  the  heart 
cycle.  The  first  sound,  produced  by  contraction  of  heart 
muscle  and  closure  of  auriculo-ventricular  valves,  is  evident- 


226  EXPERIMENT  XXXIX. 

ly  systolic.  The  second  sound,  made  by  closure  of  semi- 
lunar valves,  is  evidently  diastolic.  Therefore,  any  sound 
occurring  between  the  beginning  of  the  first  and  the  begin- 
ning of  the  second  normal  sounds  must  be  systolic,  and  any 
sound  occurring  between  the  beginning  of  the  second  sound 
and  the  beginning  of  the  first  sound  of  the  next  cycle  must 
be  diastolic. 

c.     Tiyne  Relations  of  Heart  Sounds,  the  Cardiogram  and 
Pulse  Ciirve. 

The  Cardiogram. 

The  apex  of  the  heart  comes  in  contact  with  the  wall  of 
the  chest  at  a  point  a  little  inside  of  the  mammary  line  in 
the  fifth  intercostal  space,  and  if  a  receiving  tambour  or  a 
cardiograph  is  applied  over  this  region,  where  the  apex  beat 
is  best  felt,  and  is  connected  with  a  recording  tambour,  a 
curve  can  be  obtained  which  is  the  combined  result  of 
changes  in  the  position,  form  and  volume  of  that  part  of 
the  heart.  The  form  of  the  curve  depends,  therefore,  on 
the  condition  of  the  chest  wall,  the  relation  of  the  heart  to 
the  wall,  and  the  changes  which  the  heart  undergoes  during 
its  action. 

The  cardiogram,  Fig.  43,  can  be  divided  into  five  parts, 
a  wave  caused  by  distention  of  the  ventricle  when  the  auricle 
completes  the  filling  of  the  ventricle,  the  auriculo-ventricular 
valve  closing  at  the  end  of  auricular  systole,  (see  first  dotted 
line)  ;  a  more  or  less  sharp  rise,  marking  the  period  of  ris- 
ing tension  in  the  ventricle,  between  the  beginning  of  the 
contraction  and  the  opening  of  the  aortic  valve  (see  second 
dotted  line)  ;  a  period  during  which  the  ventricle  is  driving 
the  blood  out,  the  aortic  valve  closing  soon  after  the  end  of 
this  period.  (See  end  of  0.4  sec.)  ;  a  more  or  less  abrupt  fall 
caused  by  the  sudden  relaxation  of  the  ventricle,  the  auricu- 
lo-ventricular valve  opening  at  some  point  during  the  fall 
(See  third  dotted  fine)  ;  a  period  corresponding  to  the  grad- 
ual filling  of  the  ventricle. 

The  rise  of  the  carotid  curve,  allowing  for  the  time  of 
transmission  occurs  a  short  time  after  the  beginning  of  sys- 
tole ;  and  the  descending  limb  of  the  dicrotic  notch,  which 


NORMAL  SOUNDS  OF   HKART.  22/ 

marks  the  end  of  the  systole,  occurs  in  the  course  of  the 
descending  limb  of  the  heart  curve.  The  record  of  the 
radial  pulse  would  of  course  come  somewhat  later.  The 
first  sound  of  the  heart  should  occur  at  the  beginning  of  the 
fall  of  the  wave  caused  by  the  auricular  contraction,  and  the 
second  sound  should  occur  at  the  beginning  of  the  fall  of 
the  curve  caused  by  the  relaxation  of  the  ventricle. 

Experiment. — Record  a  cardiogram  and  a  radial  and 
carotid  pulse  curve  on  a  drum  along  with  that  of  a  signal 
connected  with  a  cell  and  Morse  key.  Listen  to  heart  sounds 
and  let  one  listener  so  work  the  key  that  the  click  of  the  sig- 
nal shall  exactly  coincide  with  the  heart  sounds.  When  he  is 
able  to  do  this  well,  as  tested  by  all  the  listeners,  run  drum  at 
fast  speed  and  record  the  time  of  the  sounds  in  relation  with 
the  three  other  curves.  The  subject  should  cease  to  breathe 
just  when  the  record  is  to  be  taken,  by  holding  the  breath, 
without  straining,  at  the  close  of  a  quiet  expiration.  The 
reaction  time  to  sound  varies  from  0.15-0.20  sec,  according 
to  the  observer,  hence  to  have  the  sound  of  the  heart  and 
the  signal  coincide,  the  experimenter  will  have  to  anticipate 
the  beat,  i.  e.,  determine  the  rhythm  by  listening  a  short  time 
and  then  tap  at  the  instant  that  the  heats  are  to  he  expected. 

If  care  be  used,  a  good  picture  of  the  relative  time  of  the 
coming  of  the  sounds  of  the  heart  and  of  the  carotid  and 
radial  pulse  can  be  obtained. 

Notice  that  the  first  sound  slightly  precedes  the  primary 
upstroke  of  the  carotid  pulse  (about  .01  sec),  and  that  the 
second  sound  slightly  precedes  the  dicrotic  wave.  Also  ob- 
serve that  the  primary  wave  of  the  radial  pulse  begins  about 
half  way  between  the  two  heart  sounds.  It  is  evident,  there- 
fore, that  the  place  of  any  sound  of  doubtful  nature  can  be 
located  rather  definitely  in  the  cycle  by  its  relation  to  the 
carotid  pulse,  but  not  so  well  by  reference  to  the  radial. 


228  r;xpr;RiMi;NT  xxxix. 

DESCRIPTION    OF    FIGURE    43. 

The  diagram  assumes  that  a  normal  heart  is  beating  at 
the  rate  of  75  per  minute,  and  that  one  complete  cycle  occu- 
pies eight-tenths  of  a  second.  Each  of  the  spaces  enclosed 
by  the  unbroken  lines  is  o.i  second.  In  the  horizontal  space? 
we  see  the  duration  of  the  systoles  of  the  auricles  and  ven- 
tricles, and  the  period  of  diastasis ;  the  time  of  occurrence 
of  the  heart  sounds :  the  periods  when  the  valves  are  open, 
the  upper  blank  space  covering  the  interval  when  the  semi- 
lunar valves  are  open,  and  the  lower  blank  spaces  the  inter- 
val when  the  auriculo-ventricular  valves  are  open ;  changes 
in  the  form  of  what  may  perhaps  be  regarded  as  a  typical 
cardiogram  ;  the  waves  of  the  venous  pulse  ;  two  serial  views 
of  the  form  changes  of  the  auricles  and  ventricles  of  the 
right  heart,  the  large  arteries,  and  the  position  of  the  heart 
calves,  (the  upper  series  illustrating  the  action  of  the  heart 
with  respect  to  the  associated  waves  of  the  venous  pulse 
curve,  and  the  lower  picturing  the  relation  of  the  heart  to 
the  pressure  waves  in  the  arteries)  ;  finally,  at  the  bottom 
■of  the  chart,  a  sphygmogram  of  the  carotid  pulse.  The 
horizontal  lines  just  below  each  of  the  hearts  represent  the 
chest  wall. 

The  vertical  broken  lines  enclose  a  space  between  the 
0.1  and  0.2  second,  when  both  semilunar  and  auriculo-ven- 
tricular valves  are  closed,  (see  heart  2)  ;  and  during  the  0.5 
second  a  similar  space  is  enclosed  marking  the  interval  when 
the  ventricle  is  again  shut  off  from  both  auricle  and  artery, 
(see  heart  6). 

Of  course  the  schemes  of  the  heart  action  are  purely 
diagramatic;  the  ninth  heart  picture  of  the  lower  series 
would  be  a  truer  representation  of  the  heart.  Although  the 
right  heart  is  supposed  to  be  represented,  only  two  curtains 
of  the  tricuspid  valve  are  shown ;  the  pulmonary  artery  is 
made  to  He  in  close  contact  with  the  right  auricle,  although 
as  it  winds  around  the  aorta,  it  is  the  aorta  which  is  most 
intimately  related  to  the  wall  of  the  right  auricle ;  the  right 
ventricle  is  represented  as  forming  the  apex  of  the  heart, 
although  in  fact  it  is. the  tip  of  the  left  ventricle  that  is  the 
apex. 


NORMAL  SOUNDS  OF   HEART. 


22g 


SYSTOLE 
SOUNDS 
VALVES    OPEN 

CARDIOGRAM 


VENOUS    PUL3: 


RIGHT    HEART 


CAROTID    PUI,SH 


Fig.  43.  Diagram  of  a  heart  cycle,  showing  form  changes  of  right  side  of 
heart  in  relation  to  the  cardiogram,  the  venous  and  arterial  pulse,  and  the 
iieart  sounds. 


230 


KXPTvRIlMKNT  XXXIX. 


INFLUENCES  AFFECTING  RESPIRATION.  23I 

EXPERIMENT  XL. 
Thoracic  and  Abdominal  Movements  in  Respiration. 

Apparatus. — Mount  two  recording  tambours  and  a  time 
signal  to  write  in  a  vertical  line  ;  connect  the  signal  to  clock 
circuit ;  connect  the  two  tambours  by  special  rubber  tubes 
to  two  pneumographs,  leaving  side  tubes  open. 

Experiment. — The  subject  seats  himself  comfortably, 
then  the  cord  of  one  pneumograph  is  passed  around  his 
chest  and  the  cord  of  the  other  around  his  waist.  Tie  them 
with  a  tension  that  will  extend  the  pneumographs  about  2 
cm.  Subject  should  sit  so  as  not  to  see  the  curves  and 
should  pay  as  little  attention  to  breathing  as  possible. 

a.  Normal  Record. 

After  subject  has  remained  quietly  seated  for  at  least 
two  minutes,  place  clips  on  side  tubes,  start  drum  at  2  mm. 
per  second  and  record  curves  for  one  minute.  Natural, 
unconscious  breathing  is  what  we  wish  to  study,  and  hence 
the  subject  should  try  to  think  of  something  else. 

b.  Effect  of  Using  the  Voice. 

Record  normal  curves  for  10  seconds,  then  read  aloud 
for  30  seconds.  In  same  manner  try  the  effect  of  counting 
aloud  in  unison  with  the  ticking  of  the  clock.  Always  mark 
on  curve  the  time  when  each  test  begins  and  ends,  and  what 
was  done.  Note  the  effects  on  rate  and  character  of  the 
movements. 

r.     Inhibitory  Effects  of  Sivallozving. 

Take  normal  record  for  15  seconds,  then  let  subject  drink 
a  glass  of  water  without  stopping,  taking  record  during  the 
drinking  and  for  15  seconds  after. 

d.     Effects  of  Effort. 

In  the  same  manner  observe  the  effect  of  trying  to  hold 
two  pin  points  as  close  together  as  possible  wnthout  touching, 


232  EXPERIMENT    XL. 

for  15  seconds;  of  clenching  the  fists  as  tightly  as  possible 
for  15  seconds;  of  clenching  the  fists  as  rapidly  as  possible 
for  15  seconds;  of  pressing  the  hands  upon  the  knees  strong- 
ly for  15  seconds. 

Note  the  efifect  in  the  different  cases,  and  explain  the 
difference. 

e.     Relation  of  Rate  of  Respiration  to  Rate  of  Heart. 

Replace  the  abdominal  pneumograph  by  a  carotid  tam- 
bour ;  then  study  the  following  cases : 

(i)  Relative  rates  of  heart  and  respiration  under  nor- 
mal conditions,  sitting  quietly. 

(2)     Effect  of  mental  excitement. 

It  is  of  course  evident  that  voluntary  control  of  the 
rate  of  breathing  in  all  of  the  foregoing  tests  lessens  their 
value.  Usually  it  is  only  in  the  later  tests,  after  the  subject 
has  become  acctistomed  to  wearing  the  apparatus,  and  the 
work  has  ceased  to  be  interesting,  that  the  subject  will 
breathe  naturally.  It  is  best,  for  this  reason  for  all  the  tests 
to  be  made  first  on  one  student  and  later  on  his  associate. 


INFLUKNCKS  AFl-'CCriNG  RESPIRATION.  233 


234 


T';xi'J';rimi-;nt  xr,. 


MEASUREl\rENT   OF  EXPIRED  ATR. 


235 


EXPERniENT  XIJ. 


Measurement  of  the  Expired  Air. 


The  air  which  is  breathed  by  quiet  respirations,  the  tidal 
air,  averages  only  about  500  cc.,  and  of  this  amount,  only 
about  360  cc.  reaches  the  alveoli  of  the  lung,  the  rest  re- 
maining in  the  bronchi  and  upper  air  passages.  By  deeper 
respirations  much  more  air  is  taken  in  and  given  out,  and 
it  is  possible  by  forced  inspirations  to  breathe  in  1,600  cc. 


Vital 
Capacity 

3700 


Complemental    1600 
Forced  Inspiration 


Dead  Space 


140 


Entering  alveolse  -  360 


Tidal 
500 


Supplemental   1600 
Forced  Expiration 


Residual  1000 
Escapes  when  thorax  is  opened 


Minimal — Imprisoned  Air 


Reserve 
2600  -|- 


more,  the  complemental  air,  and  to  breathe  out  1,600  cc. 
more,  the  supplemental  air.  The  sum  of  the  tidal,  supple- 
mental, and  complemental  air,  gives  what  is  known  as  the 
vital  capacity,  3,700  cc.  Ordinarily  there  remains  in  the 
chest  2,600  cc,  the  reserve  air,  of  which  1,000  cc,  the  resid- 
ual air,  cannot  be  expelled  by  a  voluntary  effort,  but  will 
leave  the  lungs  when  they  collapse  on  the  opening  of  the 


236  EXPERIMENT  xLI. 

thorax,  and  a.  small  quantity,  the  minimal  air,  which  even 
then  does  not  leave  the  lungs,  but  will  be  imprisoned  by  the 
collapse  of  the  bronchi,  (See  i,  Exper.  XXVIII).  These 
figures  are  only  rough  averages,  and  the  values  found  for 
different  individuals  differ  greatly. 

By  means  of  the  air  breathed  we  take  in  oxygen,  and 
give  off  carbon  dioxide  gas,  water,  and  heat.  The  necessary 
gaseous  exchange  would  depend,  not  only  on  the  amount  of 
active  tissue,  but  on  the  activity  of  the  tissue.  Even  when 
no  external  work  is  being  done,  chemical  compounds  must 
be  broken  down  to  supply  the  heat  needed  for  the  main- 
tenance of  the  body  temperature.  The  loss  of  heat  is  greater 
for  a  child  than  for  an  adult,  because  the  smaller  the  body, 
the  greater  the  surface  in  proportion  to  the  mass.  Vierordt 
states  that  for  a  child  one  day  old,  the  surface  area  is  812 
sq.  cm.  for  every  kilo  of  body  weight,  and  for  an  adult  it  is 
301  sq.  cm.  The  amount  of  katabolism  and  gaseous  ex- 
change should,  therefore,  be  greater  per  kilo  in  the  child 
than  the  adult.     The  surface  area  is  calculated   from  the 

formula  12,312  x    ^/g  ,    G  being  the  weight  in  grams.    In 

adults,  the  weight  of  inactive  tissue,  bones  and  fat,  is  so 
variable,  that  the  weight  is  not  a  good  index  of  the  amount 
of  active  tissue  and  necessary  gaseous  exchange.  The  chest 
measure  may  not  give  the  story,  because  in  many  individuals, 
respiration  is  largely  diaphragmatic.  Finally,  the  vital  ca- 
pacity depends  not  only  on  the  present  need,  but  on  the  way 
the  individual  has  lived.  The  length  of  the  body  is  also  a 
doubtful  standard  of  comparison ;  never  the  less,  the  follow- 
ing table  from  Vierordt  is  quoted,  as  giving  an  indication 
of  the  way  the  vital  capacity  is  influenced  by  size  of  body. 
Experiment. — The  apparatus  will  be  understood  by  ex- 
amining Fig.  44.  Notice  that  the  air  enters  the  valve  cham- 
ber (F)  through  the  lower  valve,  passes  to  the  subject,  and 
is  given  off  by  him  through  the  other  valve  to  the  outside, 
if  the  stop-cock  5  is  open,  or  to  the  spirometer,  if  the  cock 
is  turned  in  that  direction.  On  entering  the  apparatus  it 
collects  above  the  water  and  raises  the  bell.  Caution. — When 
thf^  air  is  to  be  expelled  aki'ays  remove  the  rubber  stopper 
(C). 


MEASUREME^NT  OF  EXPIRED  AIR. 


237 


Vital  Capacity  and  Size  of  Body 


Height  Vital 

(cm.)  Capacity  (cu.  cm.) 

154.5-  157 2635 

157     -159-5   2841 

159.5  -  162 2982 

162     -  164.5   3167 

164.5  -  167 3287 

167     -  169.5    3484 

169.5  -  172 3560 

172     -  174-5  3634 

174-5  -  177 3842 

177     -  179-5   3884 

J  79     -  182 4034 

182    4454 


Differ- 
ence 


206 

141 

185 

120 

197 

76 

74 

208 

42 

150 

420 


Average  3484  

Average  for  every  2>^  cm.  of  length   iii 


a.     Tidal  Air. 

It  is  difficult  to  determine  the  tidal  air,  because  the  char- 
acter of  the  respiratory  movements  alters  as  soon  as  one 

becomes  conscious  of  them. 
Take  a  fresh  mouth-piece  and 
connect  it  with  the  apparatus, 
and  then  adjust  the  rubber 
between  the  teeth  and  lips,  so 
that  an  air-tight  closure  will 
be  obtained.  Open  the  three- 
way  cock  so  that  the  air  will 
escape  freely,  and  then  hold- 
ing the  nose,  breathe  quietly 
and  as  naturally  as  possible, 
drawing  in  the  air  through 
one  valve  and  giving  it  out 
through  the  other  and  the 
open  cock.  When  the  breath- 
ing seems  to  be  normal,  let  your  partner  turn  the  valve  at 
the  instant  you  have  finished  taking  in  an  ordinary  breath, 
and  then  continue  breathing  as  before  but  into  the  spiro- 
meter. Count  the  breaths,  note  the  amount  that  has  been 
expired,  and  calculate  the  average  tidal  air. 


Fig.  44.  Apparatus  for  measur- 
ing the  expired  air.  M,  mouth 
piece,  consisting  of  a  glass  tube  and 
a  piece  of  sheet  rubber  shaped  to 
fit  the  space  between  the  teeth  and 
the  lips ;  V,  valve  chamber ;  S, 
three-way  cock,  permitting  the  air 
to  escape  or  to  enter  the  spiromet- 
er ;  C,  cork  keeping  air  in  spiro- 
meter ;     W,     water     in     spirometer , 


238  EXPERIME^NT  XU. 

b.  Snpple'inental  Air. 

Breathe  quietly  as  before,  holding  the  nose  dosed,  and 
having  the  cock  open,  then  at  the  end  of  a  quiet  expiration, 
let  your  partner  suddenly  turn  the  cock  toward  the  spirom- 
eter, and  empty  your  lungs  as  completely  as  you  can.  Make 
at  least  three  tests.  Record  in  your  notes  the  result  of  each 
test  and  the  average. 

c.  Vital  Capacity. 

Fill  your  lungs  as  completely  as  possible  and  then  quietly 
and  steadily  breathe  all  the  air  possible  into  the  spirometer. 
Make  at  least  three  tests,  taking  the  largest  volume  expired 
as  the  vital  capacity. 

d.  Coniplemcntal  Air. 

This  can  be  calculated  by  subtracting  the  sum.  of  the 
average  tidal  and  average  supplemental  air,  from  the  vital 
capacity. 

Report  the  resu.lts  of  these  experiments  in  your  notes, 
and  try  to  find  an  explanation,  in  case  your  figures  differ 
widely  from  those  given  above. 


MKASURKMKNT  OP  EXPIRED  ATR.  239 


240  EXPKRIMENT  XT,I. 


BODY  TEMPERATURE.  24 1 


EXPERIMENT  XUT. 

Regulation  of  Body  Temperature. 

Regulation  of  temperature  depends  on  adjustment  of 
heat  production  to  heat  elimination,  or  vice  versa.  Heat 
production  results  from  the  splitting  up  of  chemical  com- 
ponds  and  oxidation  processes  in  all  active  cells,  but  es- 
pecially in  the  muscles,  because  of  their  greater  mass.  It 
is  well  knov^m  that  the  blood  leaving  an  organ  is  warmer 
than  that  entering  it,  that  the  rectal  temperature  is  higher 
after  a  meal,  and  that  it  may  be  increased  a  couple  of  de- 
grees by  active  exercise.  Heat  is  given  off  chiefly  from  the 
skin  and  air  passages,  by  conduction,  radiation,  and  evap- 
oration. It  is  believed  by  some  observers  that  there  are 
special  centers  regulating  heat  production.  The  centers 
which  control  the  flow  of  blood  to  the  skin,  the  activity  of 
the  sweat  glands,  and  the  rate  and  depth  of  respiration  reg- 
ulate the  elimination  of  heat. 

Experiments. 
a.     The  Loss  of  Heat  from  the  Skin. 

1.  The  loss  by  conduction,  noticeable  whenever  one 
touches  a  cold  object,  the  cold  points  having  their  tempera- 
ture suddenly  lowered  by  the  loss  of  heat  in  warming  the 
object. 

2.  The  loss  by  radiation,  can  be  readily  observed  by 
bringing  the  palm  of  one  hand  close  over  the  back  of  the 
other,  or  close  to  the  face,  but  without  touching  it,  and  feel- 
ing the  heat  radiating  from  the  warmer  surface ;  this  warms 
the  air,  and  the  heated  air  excites  the  warmth  spots  in  the 
skin. 

3.  The  Joss  by  evaporation,  can  be  recognized  by  moist- 
ening the  skin,  putting  the  mouth  close  to  it,  and  sucking  air 
in  across  the  surface.     Control  this  result  by  repeating  the 


242  EXPERIMENT  XEII. 

test  at  a  place  where  the  skin  has  not  been  moistened.  The 
evaporation  is  caused  by  the  heat  brought  by  the  blcod  to 
the  skin,  and  the  heat  is  lost  in  evaporating  the  moisture. 

b.     The  Loss  of  Heat  from  the  Air  Passages. 

1.  By  conduction  and  radiation.  This  can  be  recog- 
nized by  simply  breathing  on  the  skin. 

2.  By  Evaporation.  This  occurs  in  the  same  way,  and 
the  moisture  given  up  tO'  the  air  in  the  process  can  be  de- 
tected in  the  moisture  which  will  be  deposited  when  one 
breathes  on  a  cold  pane  of  glass. 

The  amount  of  heat  lost  by  conduction  and  radiation 
from  the  air  passages  and  the  skin,  will  depend  on  the 
amount  of  blood  flowing  through  the  surface  vessels,  and 
its  temperature  as  compared  with  that  of  the  object  touched, 
and  that  of  the  outside  air ;  and  the  heat  lost  by  evaporation 
will  depend  on  the  amount  of  moisture  supplied  to  the  sur- 
faces b}^  the  mucous  membrane  and  the  sweat  glands,  and 
the  degree  of  saturation  of  the  air  at  the  time.  The  body 
temperature  rises  when  the  surrounding  air  is  hot,  and  es- 
pecially when  it  is  moist  and  hot. 


BODY   TKMPKRATURE.  243 


244  EXPERIMENT  XUI. 


ARTlFlCTAIv  RESPIRATION.  245 

EXPERIMENT  XUII. 

Artificial  Respiration. 

Nornjiilly  air  is  sucked  into  the  chest  by  enlargement  of 
the  thorax  in  the  antero-posterior  and  lateral  directions, 
and  by  the  descent  of  the  diaphragm,  and  is  driven  out  by 
the  elastic  recoil  of  the  lungs,  the  walls  of  the  chest  and  the 
walls  of  the  abdomen.  The  most  usual  form  of  artificial 
respiration  used  for  animals,  is  to  force  air  rhythmically 
through  an  opening  in  the  trachea,  into  the  lungs,  by  means 
of  a  bellows  or  one  of  the  many  forms  of  air  pumps,  and 
either  to  suck  it  out,  or  more  commonly,  let  the  elastic  forces 
of  the  soft  parts  drive  it  out  through  a  valve  or  side  open- 
ing, (see  Exper.  XXIX,  c.)  One  such  form  of  apparatus,  is 
the  pulmotor,  which  is  intended  to  resuscitate  men  who  are 
partially  drowned  or  asphyxiated,  or  are  suffering  from 
extreme  shock.  The  air  or  oxygen  under  suitable  pressure 
flows  in  through  a  mask,  which  covers  the  nose  and  mouth 
and  fits  the  face  tightly,  and  then  is  sucked  out. 

Another  method  known  as  the  insuflation  method,  which 
is  used  on  animals,  forces  a  continuous  stream  of  air,  under 
known  pressure,  through  a  tube  which  has  been  introduced 
through  the  mouth  into  the  trachea  as  far  down  as  the 
bronchi,  the  air  escaping  through  the  space  between  the  tube 
and  the  walls  of  the  air  passages.  In  this  case,  the  air  in  the 
lung  is  renewed  by  diffusion  of  the  gases  between  the  upper 
bronchi  and  the  alveoli.  This  method  is  especially  of  use  in 
experiments  in  which  the  chest  must  be  opened  and  it  is  de- 
sirable that  the  lungs  should  be  quiet. 

Another  set  of  methods  try  to  suck,  instead  of  blow,  the 
air  into  the  lungs.  In  this  case,  the  negative  pressure  on  the 
outside  of  the  lungs  is  rhythmically  increased  and  decreased. 
By  one  method,  intended  to  make  operations  inside  of  the 
chest  possible,  the  subject  is  placed  in  a  pneumatic  cabinet, 
in  which  the  pressure  of  the  air  is  varied  by  a  pump,  and 


246  RXPKRIMENT   XUII. 

when  the  chest  is  opened,  the  changes  in  pressure  in  the  cab- 
inet cause  contraction  and  expansion  of  the  hmg,  and  the 
^xpelHng  and  drawing  in  of  the  air. 

Several  methods  which  require  no  apparatus,  have  been 
devised  for  artificial  respiration  of  men.  The  best  known 
■of  these  carry  the  names  of  Marshal  Hall,  Howard,  Syl- 
vester, and  Schaefer. 

By  the  Sylvester  method  the  subject  lies  on  his  back; 
one  operator  cares  for  the  mouth,  keeping  it  free  from  mu- 
cus;  &c.,  and  draws  the  tongue  forAvard,  by  grasping  it 
wath  a  dry  cloth  or  by  forceps ;  one  or  two  other  operators 
expand  the  chest  wall  by  raising  the  arms  and  swinging 
them  as  far  back,  above  the  head  as  possible,  and  then  com- 
press the  chest  by  bringing  the  elbows  against  the  sides  and 
pushing  down  on  them. 

In  the  case  of  very  young  children,  a  modification  of  the 
above  method  is  quite  effective.  The  hands  of  the  operator 
grasp  the  chest  close  under  the  arms,  and  then  alternately 
raise  the  chest  wall  by  pushing  the  shoulders  up  and  back- 
ward by  the  ends  of  the  thumbs,  and  compress  it  by  pressing 
on  the  lower  part  and  sides  of  the  chest  with  the  base  of 
the  thumbs.  The  head  can  be  allowed  to  hang  down,  so  the 
tongue  shall  fall  forwards. 

The  Schaefer  method  is  eft"ective,  and  by  far  the  simplest 
for  adults,  (a  similar  method  was  proposed  by  Dr.  Kedzie 
of  this  state).  Since  by  this  method,  the  subject  Hes  in  the 
prone  position  with  the  face  towards  the  side,  fluids  tend  to 
drain  out  of  the  mouth,  and  the  tongue,  falling  forward, 
does  not  interfere  with  the  air  passages.  The  operator 
kneels  at  the  side  or  across  the  subject,  facing  his  head.  He 
places  his  hands  on  the  small  of  the  back,  over  the  lower  ribs, 
■so  that  the  thumbs  nearly  meet  at  the  spine.  Then  keeping 
the  arms  straight,  he  swings  forward  and  brings  the  weight 
of  his  body  to  bear  on  the  back  of  the  subject ;  this  compress- 
es the  chest,  and  by  pushing  the  abdomen  against  the 
ground,  causes  the  vicera  to  force  the  diaphragm  upward. 
He  then  swings  back  and  repeats  these  movements  sloidy, 
saying  looi,  1002,  1003,  by  the  forward  swing,  and  1004, 


ARTlFlCrAI,   RESPIRATION.  247 

1005  by  the  backward  swing.  The  rate  should  be  12 — 15  to 
the  minute.  The  forward  swing  produces  an  expiration, 
and  by  the  backward  swing,  the  elastic  forces  of  the  chest 
cause  it  to  enlarge  and  produce  an  inspiration. 

Experiment. — ^Each  student  is  to  act  as  subject  and 
operator,  in  order  that  he  may  gain  a  better  knowledge  of 
where  the  pressure  should  be  applied  to  be  most  efhoient. 
Have  the  apparatus  used  to  measure  the  tidal  air 
ready,  and  let  the  subject  lie  down  on  a  sheet  of  cloth  suffi- 
ciently near  the  apparatus,  so  that  the  tube  connecting  with 
the  valve  chamber,  (F^  Fig.  44),  easily  reaches  the  mouth. 

a.  The  Schaefcr  Method. 

Let  the  operator  perform  artificial  respiration  by  the 
Schaefer  method,  in  the  way  that  both  he  and  the  subject 
recognize  to  be  most  effective.  When  the  method  has  been 
learned,  let  the  subject  breathe  as  near  as  possible  normally 
into  the  spirometer  six  or  seven  breaths.  The  amount  re- 
corded should  be  noted,  and  the  amount  of  air  that  is  given 
out  by  a  like  number  of  artificial  respirations  should  be 
measured. 

b.  Effect  of  Apnoea. 

Let  the  subject  take  15  or  20  deep,  rapid,  forced  respira- 
tions, so  as  to  thoroughly  ventilate  his  lungs  and  blood,  and 
then  immediately  repeat  the  experiment  of  measuring  the 
amount  of  air  given  out  by  artificial  respirations. 

c.  The  Sylvester  Method. 

Repeat  the  work  as  described  in  a. 

Notes. 

State  in  the  notes  the  figures  obtained  in  the  above  tests 
and  explain  any  differences  which  may  have  occurred. 


EXPERIMENT   XIJII. 


Q^pHi 


b  'Y«\  D3  V^ 


-^i/zv. 


